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thesis entitled

FEEDING HABITS OF CHINOOK SALMON
IN EASTERN LAKE MICHIGAN

presented by

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-__-_.——————

FEEDING HABITS OF CHINOOK SALMON
IN EASTERN LAKE MICHIGAN

BY

Robert Fee Elliott

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Fisheries and Wildlife

1993

ABSTRACT
FEEDING HABITS OF CHINOOK SALMON IN EASTERN LAKE MICHIGAN
BY

Robert Fee Elliott

Diet of angler-caught chinook salmon (Oncorhynchug tshagytscha) from
eastern Lake Michigan waters was examined in 1985-1986 to characterize
feeding habits following a change in the dominant forage from alewife
(Alps; pggudghargnggs) to bloater (Coregonus hgyi). Diet differed both
in content and amount depending on season, region, and predator size.
Forage use appeared strongly influenced by prey distribution and
availability, indicating opportunistic predation. Juvenile bloater
(<160 mm) were an important portion of the Chinook diet, particularly in
the southern basin, but adult bloater were conspicuously absent despite
their great abundance. Adult alewife were still a major component of
the diet, particularly in the spring, in the northern basin, and for
larger chinook. Smelt (Osmerug mgrggg) contributed primarily in the
north and perch (Berg; flgvescens) contributed primarily in the south.
In the fall, young-of—the-year forage dominated the diet. Chinook from
the northern basin consumed 2-3 times more alewife and subsequently
twice as much prey as chinook from the southern basin. Differences in
regional and seasonal apparent rations seemed to correlate with catch
rates indicating chinook may congregate seasonally in different regions

of the lake in response to prey abundance.

ACKNOWLEDGMENTS

I would like to first thank my major professor, Dr. Niles Kevern,
for his continued interest in my education. He has been very generous
with his advice, with his many insights, and with his continued
financial support of my work. I am also grateful to him for allowing me
the freedom to plug away at this thesis while continuing with other
research. I also thank the other members of my graduate committee, Dr.
William Taylor and Dr. Pat Muzall, for their guidance in my education
and for their assistance and advice. Each of my committee members was
very patient, supportive, and accommodating to the end. I thank them
especially for their efforts allowing the time extension that enabled me
to finally complete this degree.

This project would not have been possible if it were not for the
many charter boat captains, mates, sport-fishing groups, and sport-
anglers who took an interest in this project and who caught and provided
access to the fish used for this study. Their cooperation and
assistance was greatly appreciated and their dedication to the fishery
noteworthy.

Many other individuals also deserve recognition and my sincere
thanks for their assistance with collecting, processing, and entering
data for this project. Stu Kogge and Mike Nurse paved the way for this
work in 1983-1985 and introduced me to the how to's of the field and lab

work. Andy Loftus assisted substantially with the field collections and

iii

lab work throughout 1986. Dave Borgeson, Bob Day, Jeff Eibler, Pam
Tyning, and Robin Zigler also assisted in the field and Jill Poort
assisted with reading scales. Art Ostaszewski, Gwen Shavalier, and
Noreen Walch assisted admirably with the many tedious hours of data
entry.

I would like to acknowledge Dr. Scott Winterstein for his guidance
with many of the statistical analyses and Dr. Kelly Smith for providing
biological data collected by MDNR. I also thank the District Sea Grant
Agents and especially the many employees of MDNR-Fisheries Division who
have provided so many positive opportunities.

I also extend a sincere thanks to my colleges in the lab, and to
my many other fiends and extended family, especially the Lucas family in
Ludington and the Holey family in Sturgeon Bay. My special thanks to my
parents, Bob and Ann, and my grandparents, Walter and Violet, and Virgil
and Geneva, and Ami, for their sincere interest and engaging
conversation regarding my work, and for the homes they provided. The
moral support offered by all these people during various periods of this
project not only made the work endurable but the time enjoyable.

Last, I thank my wife and my best friend, Colleen, whose
contribution to this project was immense. She contributed materially to
this project in many ways such as volunteering all her weekends for two
summers to help collect the data, and editing and proofing the many
drafts of this thesis, to name just a few. Most importantly, though,
she was a constant source of love, understanding, and inspiration.

Financial support for this study was provided by the Michigan Sea

Grant College Program and the Michigan Agriculture Experiment Station.

iv

TABLE OF CONTENTS

List of Tables . . . . . . . . . . . . . . . . .
List of Figures . . . . . . . . . . . . . . . . .
Introduction . . . . . . . . . . . . . . . . . .
Methods . . . . . . . . . . . . . . . . . . . . .
Field Collections . . . . . . . . . . . . . .
Laboratory Analysis . . . . . . . . . . . . .
Data Analysis . . . . . . . . . . . . . . . .
Predator Size Stratification . . . .

Statistical Tests . . . . . . . . . .

Regional and Seasonal Stratification

Results . . . . . . . . . . . . . . . . . . . . .
Characteristics of Sampled Predators . . . . .
Characteristics of the Diet . . . . . . . . .
Digested State of Prey . . . . . . . . . . . .
Sizes of Prey Consumed . . . . . . . . . . . .
Comparisons of Apparent Rations . . . . . . .
Discussion . . . . . . . . . . . . . . . . . .
Diet Composition . . . . . . . . . . . . . . .
Effects of Prey Vulnerability . . . . . . . .

Predator-Prey Size Relations . . . . . . . . .

Relation of Diet to Forage Abundance and Distribution

Page
vii

viii

. 49

Across-lake Differences in Diet . .
Lakewide Similarities in Diet Trends
Comparisons of Ration Size . . . . .
Growth and Condition . . . . . . . .
Catch Rates and Movements . . . . .
Use of Bioenergetic Models . . . . .
Partitioning Total Consumption . . .
Prey Dynamics . . . . . . . . . . .
Alewife and Bloater Abundance . . .
Consideration of Sample Methods . .
Summary & Conclusions . . . . . . . . .
Appendix A . . . . . . . . . . . . .
Appendix B . . . . . . . . . . . . .
Appendix C . . . . . . . . . . . . .
Appendix D . . . . . . . . . . . . .

List of References . . . . . . . . . .

vi

60

62

63

64

68

7O

73

75

76

78

85

89

90

93

95

100

LIST OF TABLES

Page

Table 1. Procedure used to calculate normalize lengths (Ln)
of chinook salmon for a median sample date of
July 15' 1986. O O 0 O O O O O O O O O O O O O O O O O O 13

Table 2. Length statistics of alewife consumed by of chinook
salmon from eastern Lake Michigan, 1986. Only those
sample dates where at least three prey were measured
from at least one predator size class are listed. . . . 33

Table 3. Length statistics of bloater consumed by chinook
salmon from eastern Lake Michigan, 1986. Only those
sample dates where at least two prey were measured
from at least one predator size class are listed. . . . . 34

Table 4. Length statistics of rainbow smelt consumed by the
three size classes of chinook salmon from eastern
Lake Michigan, 1986. . . . . . . . . . . . . . . . . . . 35

Table 5. Length statistics of prey fish (all species combined)
consumed by the three size classes of chinook salmon
from eastern Lake Michigan, 1986. . . . . . . . . . . . . 36

Table 6. Formula used to convert caudal length to total
length, digested state and length to wet weight,
and volume to wet weight for the various prey types. . . 89

Table 7. The location, date, and number (by sex) of each
species of salmonine predator sampled in 1986. . . . . . 90

Table 8. The location, date, and number (by size class and
sex) of chinook salmon sampled in 1986. . . . . . . . . . 93

Table 9. Values of percent feeding, frequency of occurrence,
average number, average weight, percent by number,
and percent by weight for all chinook and for
feeding chinook in 1986. . . . . . . . . . . . . . . . . 95

vii

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6a.

Figure 6b.

Figure 7.

Figure 8a.

Figure 8b.

LIST OF FIGURES

Locations and basin divisions where salmonines
were collected from eastern Lake Michigan in 1986

(abbreviations for port names are in parentheses).

Sizes of chinook salmon sampled in 1986, and
division of the sample into three size groups,
that represent age, based on the frequency
distribution of lengths normalized to July 15. .

Number and lengths of chinook salmon sampled
during different seasons from the southern and
northern basins of eastern Lake Michigan, 1986. .

Frequency distributions of the number and weight
of prey consumed by chinook salmon from eastern
Lake Michigan, 1986. . . . . . . . . . . . . . .

Relation between the percent feeding and the
average amount of prey consumed by the three
size classes of chinook from the northern basin
of eastern Lake Michigan, 1986. . . . . . . . . .

Frequency of occurrence of prey types consumed
by size class of chinook salmon from the
southern basin of eastern Lake Michigan, 1986. .

Frequency of occurrence of prey types consumed
by size class of chinook salmon from the
northern basin of eastern Lake Michigan, 1986. .

Average frequency of occurrence of prey types
consumed by each size class of chinook salmon
from the southern and northern basins of eastern
Lake Michigan for April-October, 1986 . . . . . .

Number of prey fish consumed by size class of
chinook salmon from the southern basin of
eastern Lake Michigan, 1986. . . . . . . . . . .

Number of prey fish consumed by size class of

chinook salmon from the northern basin of
eastern Lake Michigan, 1986. . . . . . . . . . .

viii

Page

. 18

.21

.22

. 24

. 25

.26

. 27

. 28

Figure 9. Average number and percent of the number of prey
fish consumed by each size class of chinook
salmon from both basins of eastern Lake Michigan
for April-October, 1986. . . . . . . . . . . . .

Figure 10a. Biomass of prey consumed by size class of
chinook salmon from the southern basin of
eastern Lake Michigan, 1986. . . . . . . . . . .

Figure 10b. Biomass of prey consumed by size class of
chinook salmon from the northern basin of
eastern Lake Michigan, 1986. . . . . . . . . . .

Figure 11. Average biomass and percent of the biomass of
prey consumed by each size class of chinook
salmon from both basins of eastern Lake Michigan
for April-October, 1986. . . . . . . . . . . . .

Figure 12. Length of alewife, bloater, smelt, and perch
consumed by all sizes of chinook salmon from
eastern Lake Michigan, 1986. . . . . . . . . . .

Figure 13. Length of alewife, bloater, smelt, and perch
consumed by all sizes of chinook salmon from
eastern Lake Michigan, 1985. . . . . . . . . . .

Figure 14. Length of alewife, bloater, smelt, and perch
consumed by all sizes of coho salmon from
eastern Lake Michigan, 1986. . . . . . . . . . .

Figure 15. Length of alewife, bloater, smelt, and perch
consumed by all sizes of steelhead from eastern
Lake MiChigan' 1986 O O O O 0 O O O O O O O O O 0

Figure 16. Length of alewife, bloater, smelt, and perch
consumed by all sizes of lake trout from eastern
Lake MiChigan' 1986 O O O O O O O O O O O O O O 0

Figure 17. Seasonal differences in the length distribution
and number of alewife consumed by chinook salmon
from the southern and northern basins of eastern
Lake Michigan, 1986. . . . . . . . . . . . . . .

Figure 18. States of digestion observed for alewife,
bloater, smelt, and perch consumed by chinook
salmon from eastern Lake Michigan, 1986. . . . .

Figure 19. States of digestion observed for alewife and
bloater consumed by chinook collected in the
morning and in the afternoon from eastern Lake
Michigan, 1986. . . . . . . . . . . . . . . . .

ix

Figure

Figure

Figure

Figure

20.

21.

22.

23.

Average biomass of prey consumed by size class
of chinook salmon from the southern and northern
basins of eastern Lake Michigan in 1986,
expressed as a proportion of predator biomass.

A comparison of the amount of prey consumed by
chinook salmon from the eastern and western

waters of Lake Michigan (Wisconsin waters data
from Toneys 1992).

Monthly catch rates estimated for chinook salmon
from eastern and western waters of Lake
Michigan, 1986 (data from Michigan and Wisconsin

DNR creel census programs).

Estimated cumulative biomass consumed by eastern
Lake Michigan chinook as a function of
Mortality. Estimates are for April through
October, 1986, and expressed on a per age-l

recruit basis.

53

65

69

74

INTRODUCTION

Aquatic fauna of the Laurentian Great Lakes have changed dramatically
since European settlement of the region. Within the last 100 years,
Lake Michigan's fish populations have been most strongly influenced by
the introduction and invasion of exotic species, by the degradation of
habitat, and by the harvesting of fish for food -- all associated with
rapid growth of human development in the region.

Historical descriptions of the evolution of the Lake Michigan fishery
have been offered by many authors (Van Oosten 1936, Miller 1957, Powers
and Robertson 1966, Smith 1968, Wells and McLain 1972, Christie 1974,
Bailey and Smith 1981, Emery 1985, Brown et a1. 1987, Keller and Smith
1990, Mills et a1. 1993). Of great influence in the evolution of the
present fishery were the invasion of sea lamprey (zgtggmyzgn magingg)
and alewife (519g; pgeudoharengug), and the introduction of rainbow
smelt (ngggug morgax). Through competition and predation, the presence
of these exotics had substantial and deleterious effects on the native
fishes of Lake Michigan, many of which were of commercial importance.

It is generally believed that perturbations by these exotics in
combination with the adaptability of an efficient selective commercial
fishery, caused the succession of species-specific stock collapses in
Lake Michigan (Smith 1968, Wells and McLain 1972). By the mid-1950s,
and only 20 years after the sea lamprey became noticeably established in

the lake, the important large piscivores, lake trout (Sglvelinus

1

2

namaygggh) and burbot (L953 195;) had been severely depleted. Also
depleted was the once dominant pelagic planktivore lake herring
(Cogegogug artedi), the lake whitefish (g; glgpgafggmig), and six of the
original seven species of deep water chubs. Though bloater (Q; hgyi)
were later depleted for a short period in the 1970s, they were the only
member of the native chub species complex to persist through this
initial period of despeciation. Their smaller size apparently made them
both less vulnerable to lamprey predation and last targeted as a
commercial chub species.

Alewife were first noticed in Lake Michigan in 1949 (Miller 1957).
Without a pelagic piscivore in Lake Michigan, and lacking competition
from other pelagic planktivores, alewife were able to expanded rapidly
throughout the lake. By the 1960s, this exotic species that was
perceived to be of little value, accounted for an estimated 80% of the
fish biomass in Lake Michigan (Sommers et a1. 1981). In 1967, such
imbalance in the predator prey system was made graphically evident when
alewife experienced a massive die-off that drew national attention. As
in several previous years, dead alewife washed ashore, fouling beaches
and harbors, clogging municipal water intakes, and resulting in a loss
to the tourism industry of millions of dollars (Brown 1972). By this
time, control of sea lamprey had been initiated in Lake Michigan,
allowing for the potential recovery of top level piscivores. In
response, resource agencies involved with management of Lake Michigan
fisheries stepped up active management of the lake's fishery. In
addition to stocking lake trout for the purposes of rehabilitation
beginning in 1965, coho salmon (Oncorhynchug kigutch) and chinook salmon

(Q; tghggytgghg) were stocked beginning in 1966 and 1967 respectively,

3
along with steelhead (Q; mykiss), and brown trout (Sglmg trutta), to
convert the low value alewife forage into a valuable sport fishery (Tody
and Tanner 1966). What resulted was a world class recreational fishery.
Two of the larger native species, lake whitefish and burbot also
recovered and, along with bloater and yellow perch, help to support a
viable commercial fishery.

Of the several species of salmonines stocked, chinook salmon quickly
assumed dominance both anthropomorphically as a preferred sport fish and
ecologically as a major piscivore. Through continued stocking and some
natural reproduction, they reached peak population abundance in 1985-
1987 (Smith 1993) and accounted for the majority of the salmonine sport
harvest in Lake Michigan (Rakoczy and Nelson 1990, Hansen et al. 1991).

In apparent response to growing predation, alewife declined gradually
through the 1970s and then abruptly in the early 1980s, reaching lowest
levels in 1983. Although this decline has been attributed mostly to
predation by the large salmonine population (Stewart et al. 1981), a
series of colder than average winters in the late 1970s was also likely
involved (Eck and Brown 1985) as may have been an increasing commercial
harvest of alewife.

With temporary closure of the commercial chub fishery and reduced
interactions with alewife, bloater increased quickly. By 1982, bloater
surpassed alewife in measured abundance (Eck and Wells 1987) and have
since reached levels eclipsing both their historic abundance and the
high abundance of alewife in the mid 1960s. Today, rainbow smelt,
yellow perch (ggggg flavescens), and bloater represent species that

persisted through the major periods of despeciation and continue as both

4

forage for today's salmonine fishery, and as sport and commercial
species.

Prior to the bloater recovery, alewife had been the dominant and at
times nearly exclusive forage of salmon and trout in Lake Michigan (Jude
et a1. 1987, McComish 1989). With the persistent reduction in alewife
abundance and the continued abundance of bloater, the propensity for
Lake Michigan salmonines to feed on bloater has been a major interest,
and seen by many to be a key to the continued support of healthy and
abundant stocks of salmon and trout in Lake Michigan. Bioenergetics
analyses of predator demands on the reduced alewife forage of the early
1980s led several authors (Stewart et al. 1981, Brandt et al. 1991,
Mitchell and Hewett 1987) to conclude that alewife alone were not
capable of supporting the production demands of stocked salmon and trout
populations in the Lake. However, it was also apparent that if the
large bloater biomass were effectively used as forage, a large
population of predators could be supported (Eck and Brown 1985).
Particle size applications have even indicated that piscivore biomass is
lower than would be predicted based on lower trophic production,
indicating the potential for increased piscivore production if all
forage were available and used by predators (Sprules et a1. 1991).

The need to understand how predator populations were interacting with
the forage species complex following the alewife decline stimulated the
scientific community to conduct a Great Lakes wide assessment of
salmonine diets. These studies were initiated primarily through major
universities surrounding the Great Lakes with funding from the Sea Grant
College Program. The work presented here was an extension of that

effort for eastern Lake Michigan. Other results of this "Salmonid Diet

5

Study" have been reported for each of the Great Lakes (Hagar 1984, Kogge
1985, McComish 1989, Diana 1990, Brandt 1986). Early reports from
several of the Lake Michigan studies indicating that sport salmonines
were feeding selectively on the lesser abundant alewife reinforced the
concern about the ability of forage stocks to support the number of
salmonines being stocked.

Trends observed in the chinook fishery, such as declining average
weight and declining trophy weight in the catch (Hansen 1986),
increasing diet diversity (Hagar 1984, Kogge 1985), and some limited
measures of declining stomach fullness (Hagar 1984, Jude 1987) were
possible indications of forage limitation. Definitive interpretation,
however, was seriously confounded by the continuous increase in stocking
levels, an increase in fishing effort, and a likely decrease in the
average age of the catch. The continued dominance of alewife in the
diets and lack of conclusive evidence showing declining growth suggested
to some that despite their decline, alewife were still available enough
to meet predatory demands and thus continued to dominate the diets (Eck
and Wells 1987).

In the spring of 1988, a substantial mortality of chinook salmon
occurred that was most evident in the southern regions of Lake Michigan
and bacterial kidney disease (BKD) was identified as being involved.
That year, and in years since, returns of chinook salmon were and have
been greatly reduced and BKD has persisted. As an outbreak of BKD has
traditionally indicated the presence of stress, the possibility of
forage limitation was reinforced, although it was just one of many

possible contributing factors.

6

In general, the study design and data summary associated with most
diet studies have limited their ability to directly answer important
questions relating to lake wide differences in forage availability and
forage consumption over time. Contributing to this has been the
pervasive use of present composition as a means of describing diets and
the logistic difficulty of collecting an adequate sample to describe
diet on a lake wide and season long basis.

The objective of this study was to adequately quantify and describe
the diet of angler caught salmonines collected from eastern Lake
Michigan following a shift in the lakes forage composition from one
dominated by alewife to one dominated by bloater. The period of this
study, 1986, represents a time of greatest disparity between alewife
abundance (near record lows) and chinook abundance (near record highs).
As such, this work establishes a benchmark for comparison both with
prior and latter measures of forage consumption that can be of
particular importance in ascertaining if reductions in alewife abundance

have severely limited available forage for Lake Michigan salmonines.

METHODS

Fleld Collections

Angler-caught salmonines were sampled at 15 ports along eastern Lake
Michigan in October of 1985 and from April through October of 1986
(Figure 1). Permanent cleaning stations located near boat launches and
marinas provided locations for sampling sport-caught fish. At each
port, fish were sampled from as many boats as possible over all hours of
the day. As soon as anglers returned to shore and before they began
cleaning their fish, permission was obtained to examine and sample their
catch. Most anglers were interested in the research work and were
cooperative in allowing the examination of their fish. To ensure that
fish sampled were representative of the overall catch from the lake, all
fish creeled by anglers aboard an individual boat were sampled. Fish
captured inside pier heads and from rivers were not sampled as most of
these fish were returning to spawn and were no longer feeding.

Sampled fish were identified to species, measured (total length) to
the nearest millimeter (mm), weighed to the nearest 0.1 kilograms (Kg),
and examined for external marks, fin clips, and lamprey scars prior to
cleaning. Because of the interest anglers had in the size of many of
their fish, weight was usually measured in pounds (Lbs), and then later
converted to kilograms. Scale samples were taken from approximately 25%

of the fish to provide age validation of length frequencies. During

 

 

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833"” Frankfort (FR 12)
Manistee (MA 11)
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' Montague-Whitehall (MW 8)
Muskegon (MU 7)
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_ “.00. ' St. Joseph (SJ 3) 42.00.“
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3 Michigan City (MC 1)
Figure 1. Locations and basin divisions where salmonines were

collected from eastern Lake Michigan in 1986 (abbreviations
for port names are in parentheses).

9

cleaning of the fish, sex was determined visually, unusual internal
characteristics were noted, and all stomach contents removed, placed in
individually numbered whirl-pac bags, and preserved in 10-15% formalin.
The orientation of prey fish in the stomach (head up or head down) was
also recorded when possible. Occasionally, it was uncertain whether the
complete contents of a stomach were present, either because some or all
of its contents had been regurgitated (indicated by a stretched or
distended stomach), or because the stomach wall had been slit prior to
our examination. These stomach samples were not included in further
analysis of diet.

Anglers were interviewed to determine depths and water temperatures
where fish were caught, the hours fished, and the total number of fish
caught. General weather, lake, and fishing conditions were also

recorded.

0 a s s

In the lab, prey items from each stomach were identified, assigned a
digested state value, measured (total length when possible) to the
nearest mm, and weighed to the nearest 0.1 grams (gr). Identification
was to species for fish and common invertebrates, and to order for less
common invertebrates.

As many prey fish were well digested, characteristics of scaling
pattern, lateral line musculature, pyloric caeca, carapace bones, and
vertebra were used to verify species. If identification was uncertain,
contents were classified as unidentified. This accounted for less than
6.5% of the fish. As an index of when the predator had consumed the

prey, each prey item was assigned subjectively to one of five groups:

10

intact and undigested (1), less than 25% of body mass digested but some
flesh digested (2), between 25% and 75% of body mass digested (3), more
than 75% of body mass digested but some flesh remaining (4), and only
bones remaining (5). These groupings were consistent with those used by
Kogge (1985) and Nurse (1986). Because determining total length of each
prey item was sometimes difficult because of the digested state of the
prey, standard length was often measured or estimated based on the
vertebral column length, and converted to total length using equations
developed from whole fish (Appendix A). When large numbers of
invertebrates were present, their total weight was used to estimate
their number based on weight of a known number of individuals from that
stomach. Volume (by water displacement) was also measured (nearest
milliliter) for representatives of each prey type and digested state.
These methods were generally consistent with those used by Kogge
(1985) and by Nurse (1986) for diet studies of eastern Lake Michigan
salmonines conducted in the three years preceding this study. However,
no measure of prey mass (weight or volume) was measured in 1983 or 1984,
and volume (but not weight) of prey was measured in 1985. So that
complete comparisons of diet parameters could be made among all four
years and to facilitate comparisons with other studies, relations among
length, digested state, and wet weight of prey were used to estimate
weight of prey for the 1983 and 1984 data. Relations between volume and
wet weight for each prey species (Appendix A) were used to estimate
weight of prey for the 1985 data, and to estimate volume for all prey

items collected in 1986.

11

Da a An 3

Other studies of Lake Michigan salmonines have shown diet to differ
with predator size and among regions (Jude et al 1987, Kogge 1985,
Stewart and Ibarra 1991, Miller and Holey 1992, Toneys 1991).
Preliminary analysis of these data confirmed these observations.
Because of the large sample size of this collection, an effort was made
to base all stratification of the data on both observed differences in
diet and natural biological or physical characteristics that
distinguished samples from one another rather than on arbitrary

divisions.

Predator size stratification. It was initially apparent that the size
distribution of chinook sampled differed between season and region, and
from other studies. It was therefore not only desirable, but necessary
to separate chinook into size classes so that valid comparisons could be
made. Dividing salmon into size classes is somewhat complicated by
their typically fast growth, particularly if fish are sampled throughout
the growing season. If fixed season-long size divisions (such as <50
cm, 50-85 cm, and > 85 cm) are used, many fish that would be classified
into one size group in the spring, would grow into the next size group
by fall. This can change the age structure of the size class over
time, and confound seasonal effects with age or size effects.

To avoid this problem, apparent growth rates and length frequencies
of sport-caught fish were used to divide chinook into size classes that
were representative of the seasonally increasing average size of age-1,
age-2, and age-3 and older chinook. Scales from 1986 were aged as

described by Seelbach and Beyerle (1984) and following methods developed

12

for chinook by D. Anson and S. Lazar (Michigan Department of Natural
Resources, Fisheries Division). Back-calculation of size at annulus
formation was used to verify the determined age. Straight line
regression was then used to calculate apparent or population growth
rates (Ricker 1975) for each age class sampled in 1986 and for chinook
sampled from the same waters by the Michigan Department of Natural
Resources (MDNR) biological sampling program for 1986-1989. Age data
from prior years were not included because of inaccuracies in aging
mature fish (K. Smith, MDNR, personal communication). Calculated
apparent growth rates for the 1986 MDNR-aged fish and the fish collected
during this study produced similar results, confirming that both samples
were from the same population. Using the apparent growth rates
calculated for MDNR-aged chinook collected in 1986, length for all
chinook sampled for diet in 1986 was then normalized to July 15 (the
median date) as described in Table 1. This procedure simply calculated
an apparent growth rate for each fish depending on its size and time of
capture. The rate, proportionally based on the apparent growth rates of
known-aged fish, was used to calculate the size the fish would have been
on any given date.

A frequency plot of chinook lengths normalized to July 15 revealed
three distinct modes (Figure 2). The low points between each mode
established the division of chinook into three size classes. These
divisions, although not entirely representative of all age-l, age-2, and
age-3 and older chinook, were representative of the average size of each
age class, and precluded the growing of fish from one size division into
the next during the season. These divisions were consistent for both

sexes, and for fish collected from all sampling locations.

13

Table 1. Procedure used to calculate normalize lengths (1%) of
chinook salmon for a median sample date of July 15, 1986.

Ln=Lx+(G*(Dx-Dn)

when:

G = HLx - Ls) / (Lb- L8) * Gb1+ [(Lb- Lx) / (Lb - Ls) * Gs]

calculated length in cm of fish on normalized date

individual daily growth increment

observed length in cm on day of capture

capture day of year (1-365) for the given fish

median day of year (1-365) used for normalizing length

average length of the nearest larger age class on capture day
average length of the nearest smaller age class on capture day
aparent growth rate of nearest larger age class

aparent growth rate of nearest smaller age class

average length (Lab) and apparent growth rate (Lab) for each age class
in 1986 are described by the following functions:

average length day of year (1-§§§2 grgggn [age constant
Age 0.1 chinook: S = D * (0.1087) + 23.0
Age 0.2 chinook: S = D * (0.0674) + 53.5
Age 0.3 chinook: s = D * (0.0404) + 74.7

All fish larger than the average length of age-3 fish were assigned
the apparent growth rate of age-3 fish since the apparent growth rate of
age-4 fish did not differ significantly from age-3 fish in all four

years.

14

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15

Statistical Tests. Because of the high degree of variance among
samples, statistical tests made use of paired samples whenever possible.
Wilcoxon's Signed Rank tests were used to test differences in diet
between predator size and sex. Wilcoxon-Mann-Whitney two sample tests
were used to test differences in diet between locations. T-tests were
used to measure differences in prey size consumed by predator groups.
Chi-square tests of independence were used to test differences in the

digested state of prey and in the percent of predators feeding.

Regional and Seasonal Stratification. Tests among locations, and
examination of the data, indicated that a significant and consistent
difference in diet existed between fish from the northern and southern
regions of eastern Lake Michigan (p < 0.05). The best division of the
study area was into two regions north and south of Little Sable Point at
approximately 43°40' of latitude. Since this division coincided with
the batheometric division of the lake into the southern and northern
basins (Mortimer 1975), it had both statistical and physical merit.
Though further divisions could have been made based on diet, differences
could not be solely attributed to location effects as opposed to season
effects.

Samples were then grouped by week and chi square tests of
independence (p < 0.05) performed to determine differences in percent
feeding, and in the number and type of prey consumed for samples
collected on the same week. On only 2 of 61 occasions did diet differ
for samples from the same week (within a basin). For these samples,

descriptive statistics of diet were averaged to provide weekly values.

16

Samples that did not differ, were combined by week and then descriptive
statistics recalculated.

Descriptive statistics of percent feeding, frequency of occurrence,
average number, average weight, percent by number (fish only), and
percent by weight for each prey type, and for all prey combined, were
used to describe the weekly diet for each size class of chinook from the
two regions. Since sample size was usually adequate for weekly samples,
and since preliminary analysis showed variation between weeks was often
great, no further summary of diet into monthly or seasonal periods was
justified. Generalizations about seasonal diet were based on observed
trends from several concurrent weeks.

Average diet over the entire season was calculated by averaging all
weekly values for each size class by basin over the period that data
were collected. Values for weeks where no data were collected for a
particular size class were estimated by averaging the data of the two
closest weeks (one before and one after the missing week). If several
weeks were missing, proportionally greater weight was given to the week
closer in time to the missing week. In this manner, average seasonal

values were not affected by differences in weekly sample sizes.

RESULTS

Characteristics of Sampled Predators

In 1986, a total of 3,472 salmonines were sampled. Chinook salmon
accounted for 56%, lake trout 22%, coho 14%, steelhead 6%, and brown
trout 2% of the collection. Samples were collected on 74 of the 204
days between April 5 and October 25 at up to 4 of the 15 ports each day.
Collections are listed by species, sample date, location, and sex in
Appendix B and also by size group for chinook in Appendix C. This
sample represented 0.38% of the total estimated harvest of these species
from Michigan waters of Lake Michigan in 1986.

Sex ratios for lake trout, coho, steelhead, and brown trout did not
differ significantly from a 1:1 ratio (p < 0.05), with lake trout
showing the largest percentage of males (53.6%). For chinook, males
were a significantly larger prOportion of the size-l sample (60%) than
the size 2 (49%) or size 3 (46%) samples (p < 0.05), a condition that is
likely related to the early maturing and return of many age-1 (jack)
males to their rivers of origin.

The number and distribution of sizes (and presumably ages) of chinook
sampled differed both between basin (region) and season (Figure 3).

Most of the chinook sampled in April and May were caught in the south,
most sampled in June and July were caught in the north, and in August
through October, fairly equal numbers came from both basins. The sample

from the south was dominated by size-2 chinook and from the north by

17

18

 

 

 

 

 

 

  
 

 

 

 

3° 7 North (totaln =1130)
South (totaln = 826)
20 April-May
1° i
“#9; ’ f §.s:§ I .‘ ==198
0 II II mu
m I—
8 2° *
Z; 10 —
h-
é I gII ' I ":3 ”=4”
5 o .I III III . "= ‘32
30 i—-
20 _ August-October
10 3
0 II "=33
20 30 70 80 90 100 110

Length Interval

Figure 3. Number and lengths of chinook salmon sampled during
different seasons from the southern and northern basins of
eastern Lake Michigan, 1986.

19

size-3 chinook through all months. More size-l chinook were collected in
the south, where they were equal in proportion to size-3 chinook from
June through October. Very few size-1 chinook were caught in April and
May in either basin. These trends were fairly consistent from 1983-
1986, although size-1 and size-2 chinook were a greater proportion of
the catch in 1986 than in 1983-1985. Fewer very large chinook were
collected in 1986 than in the earlier years.

Apparent growth rates calculated from aged fish from the creel showed
only minor, if any, differences between 1986-1989. Despite apparent
changes in fishing effort, harvest, mortality, forage availability, and
possibly growth, modes in the normalized length distributions of chinook
for 1983-1986 (including the points of division between the modes)
showed no obvious shifts between years, although the size-3 mode
encompassed larger fish in earlier years.

For 1986, water temperatures at depths where chinook were captured
(reported by anglers) were consistent between basins, increasing from
5-7 °C in April to 9-13 °C by the end of May. Water temperatures where
chinook were captured remained between 9 and 13 °C from June through
October. These similarities indicated direct comparisons of diet
between regions and across seasons should not be confounded by potential

temperature effects.

thgagtgglgtlgs of the Diet

A total of 1,956 chinook stomachs were examined in 1986. Of these,
1,070 contained food, 860 were empty, and 26 were of a questionable
state (described previously) and were not included in further analysis.

Overall, the distributions of prey weight and prey number per stomach

20

followed a poisson-like distribution (Figure 4). Most stomachs
containing food had small amounts while fewer had full stomachs. A
similar distribution was reported by Diana (1990), indicating this was
typical at least for Great Lakes chinook. The 860 empty stomachs also
fit the same poisson distribution, indicating that the state of being
empty was just a continuation of the distribution of feeding levels
observed.

Random variation within samples (among fish) was high, so that for
small samples, differences were not easily interpreted. Comparison
between large samples indicated that variation in the frequency of
occurrence, in the amount consumed, and in the size of prey consumed was
generally greatest between dates, less between sample locations on a
given date, and least between size groups within samples. Because of
the variation between dates, generalizations about seasonal diet
characteristics were made based on observable trends from several
sequential samples.

Within size classes of chinook, there was a direct, although weak,
relationship between the percent of fish feeding and the amount of prey
consumed (Figure 5). This, relation, along with the earlier described
fit of empty stomachs to the poisson-like distribution of consumed prey,
indicated that it was appropriate to combine fish with empty stomachs
with feeding fish when calculating diet parameters. Trends observed in
the amount and composition of diet for all chinook, and for feeding
chinook only, were generally the same, differing only in magnitude.
Calculated values of percent feeding, frequency of occurrence, average
number, average weight, percent by number (for prey fish only), and

percent by weight for each prey type are presented for all fish, and for

21

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23
feeding fish only, in Appendix D.

Diet of chinook salmon varied seasonally, differing among predators
of different size and between predators from the north and south basins.
Trends in the diet were similar for frequency of occurrence of prey
types (Figures 6a, 6b, and 7), number of prey fish per chinook stomach
(Figures 8a, 8b, and 9), biomass of prey per stomach (Figure 10a, 10b,
and 11), percent number (Figure 9), and percent biomass (Figure 11).
Seasonal and regional differences were related to prey distribution,
availability, and size (Tables 2-5, Figures 12-17). There were no
observed differences in diet between sexes other than in the fall for
size-3 chinook, when males had a small but significantly higher
incidence of empty stomachs (p < 0.05).

Alewife occurred in the diet in the spring and summer as adults and
yearlings, and in the fall primarily as young-of-the-year (YOY). They
were the dominant prey found in age-3 and larger chinook from the
southern basin and in age-2 and age-3 and larger chinook from the
northern basin. Sizes of alewife consumed ranged from 20-240 mm,
representing all sizes of alewife typically found in the lake. The
frequency, absolute amount, and proportion of alewife in the diet
increased with predator size in both basins, but was much greater in the
north than in the south. The amount of alewife in the diet was
responsible for a much larger amount of prey per stomach (referred to
hereafter as apparent ration) observed for all size chinook from the
northern basin.

Bloater occurred in the diet primarily from July on as juveniles and
young adults less than 160 mm in length. They were the dominant prey

found in age-1 and age-2 chinook from the southern basin. The

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27

Sizes

 

 

 

 

 

Skez

Number of Pray For Stomach

Size 1

 

 

 

 

m YELLOW PERCH UNIDENTIFIED FISH
RAINBOW SMELT 333333 OTHER FISH SPECIES

BLOATER CHUB
ALEWIFE

 

  

 

 

 

Figure 8a. number of prey fish consumed by size class of chinook
salmon from the southern basin of eastern Lake Michigan,
1986. The number above each bar indicates the sample size.

28

Sizes

)8

 

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1

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Skez

 

Number of Prey Per Stomach
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I BLOATER CHUB
ALEWIFE

Figure 8b. Number of prey fish consumed by size class of chinook
salmon from the northern basin of eastern Lake Michigan,
1986. The number above each bar indicates the sample size

 

YELLOW PERCH UNIDENTIFIED FISH
RAINBOW SMELT 333322;? OTHER FISH SPECIES

 

  

 

 

 

 

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29

   

UNIDENTIFIED
OTHER

 

 

 

 

Size 1 Size 2 Size 3

 

 

 

 

 

 

 

Size 1 Size 2 Size 3 Size 1 Size 2 Size 3
|——— South Basin ———J ; North Basin ——_J

Average number and percent of the number of prey fish
consumed by each size class of chinook salmon from both
basins of eastern Lake Michigan for April-October, 1986.

30

Prey Biomass Per Stomach (grams)

 

 

 

—APFi-—I— MAY—J— JUN -—I—JUL—I—AUG—I—SEP-

I BLOATER CHUB YELLOW PERCH - UNIDENTIFIED
ALEWIFE m RAINBOW SMELT m OTHER (Z=zoop. |=insects)

Figure 10a. Biomass of prey consumed by size class of chinook salmon
from the southern basin of eastern Lake Michigan, 1986.
The number above each bar indicates the sample size.

31

 

Sizes

Sizez

Prey Biomass Per Stomach (grams)

 

Size 1
1 5

10

 

 

 

o . . .
I I I
I—MAY—I— JUN -I— JUL —I—AUG—I— SEP —L— oer—I

BLOATER CHUB 2322355522313: YELLOW PERCH ‘ ‘ UNIDENTIFIED FISH
ALEWIFE RAINBOW SMELT 3:323:53 OTHER (mostly zooplankton)

 

 
  

 

 

 

 

 

Figure 10b. Biomass of prey consumed by size class of chinook salmon
from the northern basin of eastern Lake Michigan, 1986.
The number above each bar indicates the sample size.

32

- UNIDENTIFIED

 

 

 

   

 

 

 

OTHER
PERCH
22 /’ SMELT
20 /- BLOATER
1a /_ ALEWIFE
E 16 /_
g 14 /
O) _
a 12 /
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g ..............
a 6 /
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2 V
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Size 1 Size 2 Size 3 Size 1 Size 2 Size 3

Percent of Prey Biomass

 

 

 

 

 

 

 

   

 

Size 1 Size 2 Size 3 Size 1 Size 2 Size 3
SouthBasin ——l L——_— North Basin ——_1

Figure 11. Average biomass and percent of the biomass of prey
consumed by each size class of chinook salmon from both
basins of eastern Lake Michigan for April - October, 1986.

 

 

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van IIha NIv a0 DInON had .Ivn no ONH .INo 0.5 On «Icon and IOB mN I I I I I o
«as ..oo “.0 an «.oa oou .Iao «a I I I I I o I I I I I o
no” .Ioufl «.a so ..~vn «on .Is. a” «as .Inns e.«s so v.uvs man .va on I I I I I o
"as ..nos a." «a o.n- so" .Ip. a. "as ..mo a.» so o.oa no" .Inn an I I I I I o
no” ..ovs a.n «a v.vns on" .IFHH as an" ..o- p.o n. v.av~ vs" Ina" n I I I I I 0
en" .Ieos v.0" an a.ouu eon In» o I I I I I o I I I I I o
nan .Iflns o.v an a.~v~ "an .Inofl as I I I I I o I I I I I o
«HIdIIoon .Indd. mwlm lad: lay—l ”I j . .m ImIn. Igdl Iomqwmi ml 411% .n. ma o>< 0 so ml
n ”NHm _ r N fluHm _ F H fluHm _
.oosao oeao xoocano coozuon ouomuao ouao uouoo~n ouocs oodmaso ooosu nousoaoca usou oaom .vounda

one anode onus uousmoum oco nosoa as Scam cousoooe ouoz Noun ooucu unsoa us onus: nouso oamaso
.omma .coo«noaz oxen snouooo scum coaaso xoocano an coasocoo oud3oao uo oowuodusuo cannon

Eco

A4808
uuxon On
onxon on
hN\ao Nd
thoo an
HNxao o
ON\ao o
0n\ao on
vH\ao on
moxao nu
onxoo N
vaoo nn
VNxoo Na
nN\oo an
NN\oo an
hn\oo o
anoo On
a0\oo v
ooxoo a
anho Nd
NNxho nu
anxho on
ou\po an
Haxho n
moxpo an
mN\oo ma
na\oo On
Nnxoo on
n0\oo o
Hn\no o
vN\no Na
vN\mo a
nn\no Ha
Hfi\no on
o«\mo Nu
voxno o
nO\no OH
0Nxvo N
ON\vo n
GN\vo o
MalddI a

. N manna

34

 

 

 

hOH I ha h.N vv O.HOH hMH I on no no no o.H No N.om nHN I no hoH HOH I nO O.N ov a.om onH I.mn ONH
I I I I I O I I I I I O Hh I no n.H h v.0o Oh I.Oo h
I I I I I O on No H.0 Nn N.oo 00 I.nv v on I Hh o.N NH o.0h 00 I Hp m
I I I I I O nOH v0 O.v VN N.no NHH I Nb a I I I I I O
I I I I I O I N.n a m.na OOH I HO N I I I O.NOH I H
I I I «.mnH I H I 0.0H ON 0.05 nu I no N I h.n oH O.NNH nnH I.OHH N
I I I I I O no Hh N.n Hn O.n0 OHH I.Ho a oHH I No 0.0 0v 0.00 OHH I oo o
I I I I I O I v.0 H m.vo no I do N I I I OIoh I H
I N.H n n.Nh Oh I Hh N I I I I I O I N.n a m.Oh up I oo N
I I I I I O I o.HH nn N.OO mHH I N0 N I I I O.oh I H
I I I O.VNH I H I n.oH ov OIOOH nNH I.hh N I n.m nH o.0vH onH I HVH N
I I I I I O I I I O.HHH I H OOH I so n.v bN 0.5a nHH I.hh O
I I I 0.0NH I H Ha on H.0 oo N.Nh OHH I ov 0 so I no v.5 av o.mh nnH I.Hn HH
I I I I I O I I I n.an I H oNH I.NOH n.n oN h.nHH onH I.na o
oOH I no 0.N HH n.ho oOH I No v nOH NO 0.H h h.ho NOH I.NO v I I I O.mO I H
I I I O.oh I H I I I I I O I a.v OH 0.00 nOH I.Ha N
NNH ..HOH O.n no H.HHH OVH I oo 0H HnH Mp H.NH H0 H.nOH nHN I.ho HH nHH I Na o.v 0N n.NOH 0HH I.N0 h
on I no «.0 v N.om OOH .Ivo n HOH no N.H o 0.0a mOH I NO nH I I I OInOH I H
I I I o.Oh I H VHH HOH n.n Hn v.hOH onH I nh NN ONH I.NOH O.v nN v.HHH OnH I On OH
I I I I I O I I I O.HOH I H oOH I h0 N.n nH n.oO mOH I.OO o
I I I I I O ONH 00 h.n nH O.vOH OHH .Ino n I N.a oN O.mNH onH I NHH N
I I I 0.0nH I H I 0.N 0 0.0HH nNH .InHH N I I I I I O
I I I I I O NNH on h.m Ho m.OOH 0oH I Hh nH NVH I Oh o.nH 00 n.oOH OnH I.nn 0
I I I I I O I I I O.NO I H OHH I H0 0.n nH H.ho oOH I on n
OOH I 00 0.H 0 b.1a NOH I on n OOH va N.H HH O.NO NOH .IOO ON I I I O.NOH I H
nOH I oN n.OH ho v.OOH hnH I no n I I I I I O I I I n.N0 I H
noH I O0 5.0 on OImNH NvH .IoOH n I I I I I O I I I I I O
I 0.nH an n.ONH 0vH .IOOH N I n.N h n.oo on I no N I I I NomnH I H
on I hp n.n oH N.h0 OOH I.hh m I I I O.o0 I H hHH I on o.n NH h.HOH OHH I ma n
I I I I I O I I I I I O 00H I.00 h.v OH H.vo oOH I N0 v
I I I 0.0HH I H I h.n OH N.v0 on I as N I N.nH no nIno mHH I Nb N
I I I I I O I I I I I O onH I no 0.0 an n.OOH onH I 00 v
I I I O.NNH I H I I I H.HNH I H on I N0 h.n OH N.Oa NOH I on F
I I I I I O I I I O.o0 I H HOH I H0 v.N 0 H.Ho ho I.00 n
I I I I I O OHH v0 O.m oN n.HOH NNH I v0 n .I m.h HN h.Ha NOH I H0 N
on I O0 O.n nH O.h0 HOH I Oh o 90 0h v.N nH O.n0 on I on h I I I I I O
I I I I I O On Hp N.n vH o.00 on I no n I I I I I O
I I I I I O ooH 0n O.HH Ho h.OOH NNH I.OO n HOH I N0 n.v HN n.Ha oOH I on o
I I I 0.05 I H I 0.H m n.oh on .Ivh N I I I I I O
.H.u 0.3 «India add Ian IIomsIsImII ml jlolmlwl amnwi oImIM o>< IduiaawII ail . . oma j mud lal IIQUIcIflI mi
n fluHm __ N NNHm _— H fluHm
.uounna
OH“ OOGHO ONAO HOUGUOHQ OGO HDGOH HQ EON“ UOHQQGOB 0HO3 %0HQ O39 DOUGH #6 0H0£3 OOHGU OHQEUO
%HGC .OQGH sCflOdSOdz OXGQ GHOHNUO BORN GOEHGO XOOGHZO in UGESOGOU HOUGOHD HO QOHHDHUGUI SHDGOQ

«309

mN\OH
HH\OH
OH\OH
hN\mO
>N\OO
HNan
ON\OO
oH\aO
vH\OO
OO\OO
hoxoo
ooxoo
on\0O
vaoo
NN\OO
thoo
oH\OO
oH\OO
nH\OO
OH\0O
OOxOO
OO\OO
NO\OO
HO\OO
nN\hO
ON\hO
NNth
OH\hO
0H\hO
hH\hO

v v 0 n H N N n
o H H o H H H H
B‘\'\'\‘\'\‘\'\'\
a m o o h h h h 5
00000000

. n @HanH.

OH
OH
OH
NH
HH
o
0
OH
OH
nH
v
n
N
NH
HH
o
OH
n

HOME!"
HHHHH

35

 

 

 

 

5OH I 0O n.N an O.NOH oNN I Ho O5H H0 I O5 0.N n0 oom5 nOH I.mN nNN oo I Hm n.n o5 0.50 NnH ON nNH
oNH I 00 o.o oN n.oOH oHH I.n0 o I I I I I O I m.N 5 o.oo oo no N
I I I I I O I N.nn on 5.Ho OnH I.mo N o0H I.O o.oN 00 0.55 0nH oo n
I 0.0 oN n.noH onH I NnH N I m.on nOH 0.50 ooH I.oo N I I I I I O
I I I n.5n I H I I I I I O I I I I I O
OOH I.n5 O.5 n5 v.0. noH I.No HN 0o 1 an m.N Hn mono NHH I.Oo oo Ho I on O.H OH oo0n Nn 5n nN
oNH I n0 o.O On 0.oOH mnH I on 5 0NH I oHH o.n no O.HNH 5oH I.0o oo 0NH I 5OH o.o 0n o.5HH 5oH o5 0H
I 5.0 oN N.NnH ooH I ONH N I I I I I O I I I O.NmH I H
I I I n.Ho I H no I oN 0.0 no o.oo nOH I.ON 0 I I I I I O
I a.0 nN o.HNH onH I.OOH N NoH I HOH H.nH no o.HnH 00H I.oO 5 I I I 5.oHH I H
I N.5N 55 O.N0 ONH I.oo N I I I I I O I I I o.ooH I H
I I I I I O 0n I on n.O m O.5n no I Nn O5 no I Nn O.N nH 0.0o 5o Hn m
I I I o.onH I H I I I o.0oH I H NNH I n5 5.0H Nn n.5o NNH oo o
ONH 1.0. 5.5 oo DINOH HoH I.o5 a O5H I.OH 5.0H no o.oo ONH n.no n 50 I.nn 0.0 NH 0oon no ON No
I I I I I O I I I I I O 0HH I.O o.HN on Hoom OmH ON m
00H I 0O m.N No H.nOH ooH I no H5 HnH I 5OH 0.m 5o 5.0HH ooH I.o0 5H ooH I no o.o nn n.mOH OHH n0 n
I I I I I O I I I n.OOH I H ON I NN N.H 5 O.mN On ON 0
I I I I I O 50 I on N.m 5n n.no OHH I.Oo nH I I I I I O
an I oo 0.0 nN o.H0 on I oo o I I I I I O I I I I I O
nHH I 05 0.0 oo o.om NoH I 5o 0 I N.oH oo n.OOH ONH I.O0 N I I I I I O
I I I I I O I I I I I O I n.HH Nn N.o0 mOH n5 N
OHH I O0 n.5 on N.oOH 00H I no oH I N.0H N0 H.oOH NnH I O0 N I n.o 0H O.N0 NO o5 N
I I I N.nOH I H I I I I I O I I I I I O
I I I o.nNN I H I I I n.NnH I H I I I I I O
aOH I 0o 5.o oH 5.00 OOH I O0 n I I I I I O I I I I I O
I o.oo NnH O.NNH mOH I no N I I I I I O I I I I I O
I 0.0n OHH o.ooH 00H I 00 N I I I I I O I I I I I O
OHH I o0 n.n NH n.nOH HHH I on n I I I O.5NH I H I I I O.mOH I H
I I I I I O I I I O.HOH I H I I I I I O
I I I 5.5o I H I I I I I O I I I I I O
I I I I I O I I I H.OHH I H I I I I I O
I I I I I O I O.NH on 0.55 on I oo N I I I I I O
I I I m.onH I H I I I I I O I I I I I O
I I I I I O I n.n mH o.oNH NnH I 5HH N I I I I I O
I I I I I O I I I o.0NH I H I I I I I O
I O.o oH O.5NH onH I ONH N I I I I I O I I I I I O
I I I H.NOH I H I 0.0 N O.Ho no I Ho N I I I n.5n I H
j mm la 0 so ml .H.u one .06 mam I.OH/4|. Ilmmfll .II THIulfioI j HI
n HuHo IL _ N NNHm _ _ H fluHm _

§00390Q UHOHHHQ ONHO ”H080 0M0£3 DOHQEUO OQOSU GOUUOHUCH 0x0“ 0H0“

.oosHo onHo gooano

.mmmH .cnmnsoez oxen assumes

scum coaHoo xoocHno mo oooosHo ouHo oousu on» Na oossocoo uHoao soncHsu uo oOHuoHuouo suucon

HGHOH
5N\OO HH
HN\OO o
ON\OO 0
OH\OO m
oH\aO OH
oH\OO OH
oH\OO O
OOxoo oH
OO\OO nH
50\OO o
oO\OO n
oN\0O nH
oN\0O NH
nN\OO nH
NN\0O HH
5H\0O o
oH\0O n
OH\0O oH
OO\0O 0H
OO\OO n
0O\0O 0H
HO\0O 0
0N\5O NH
oN\5O oH
nN\5O nH
NN\5O nH
OH\5O OH
5H\5O O
mO\5O HH
oH\oO n
HO\oO o
Hn\nO o
oNme NH
5H\nO n
HH\mO OH
nO\nO OH
gm
.v manna

36

 

I o.oo NnH 0.0NH OOH I no N I N.0 nN o.oO 0OH I n0 N I I I I I O nN\5O nH
00H I NO 5.nH 50 n.nNH OOH I no OH O5H I Ho O.oH on H.OHH OoH I 50 n I I I N.0nH I H NN\5O nH
00H I oo n.ON H0 O.oNH noH I O0 o I I I I I O I I I I I O HN\5O nH
ONH I NO o.o H0 N.oOH OOH I 55 OH o5H I oo n.OH o0 N.0HH OOH I n0 0 HHH I 50 O.o 0H 0.00 OHH o0 n OH\5O OH
HoN I oo 0.on 5oH n.OmH mHN I oN o I I I O.nNH I H 0OH I 00 5.o OH H.oO oOH N0 o 0H\5O HH
I I I O.HOH I H I I I I I O I I I I I O 0H\5O OH
I H.N o O.5mH ooH I onH N I I I I I O I I I I I O 5H\5O OH
I I I 0.0HH I H noH I on 0.5H H5 0.00H O5H I O5 o I N.nH no n.nO OHH N5 N 5H\5O O
I I I I I O I I I I I O HnH I N5 0.0 oo o.HOH onH H5 0 nH\5O o
NoH I on 5.0H 5n O.nO NNH I N0 n oON I 5O n.NH no o.OOH n5H I HNH n oOH I n. o.o 0N oonO 5HH m5 0 NH\5O n
I I I I I O I I I 0.00 I H HOH I H0 o.N 0 H.HO 5O 00 n NH\5O o
N5H I oHH 0.0 On O.noH 55H I nNH o OHH I GO o.o nN n.OO NNH I o0 5 I 0.5 HN 5.HO NOH H0 N HH\5O n
OOH I oO n.n Oo 0.00H o0H I 0o 0o OO I 00 o.n on N.NO ooH I oo ON I I I I I O nO\5O HH
I I I N.ooH I H I I I I I O I I I I I O ONxoO H
ONH I O0 o.0 O5 5.NOH mON I no NN OHH I nO m.o 0m O.HOH m0H I 50 No I I I I I O anoO nH
I I I I I O OO I H5 N.n oH o.O0 OO I Oo n I I I I I O 0H\oO o
I I I I I O onH I N0 0.0 on o.OOH 5NH I O0 o oOH I o0 N.o oN O.nO oHH o5 0 onoo 0
I I I I I O 00H I 5O 5.NH No O.nNH n5H I 05 o I I I I I O nH\oO OH
I I I I I O I I I I I O I I I o.o5 I H onoO 0
H5H I oHH O.NH o5 O.noH O0H I HO OH I I I I I O I I I I I O NonO OH
I I I I I O onH I 0n 5.oH oO O.mO n0H I HO 0 I I I I I O HO\oO o
I I I I I O I I I 0.05H I H I I I I I O HO\oO 0
onH I oHH H.5 Nn 0.onH 00H I 00H m OmH I 5O o.nH o0 0.5NH n0H I no OH I I I I I O annO o
I I I O.NnH I H NNH I oo n.NH o5 O.oO n5H I Oo O I I I I I O oN\mO NH
I I I I I O NoH I 55 O.oH Oo o.OOH noH I N5 o I I I I I O oanO O
I O.5H Hm n.noH H5H I ONH N I I I O.onH I H I I I I I O nN\nO 5
I o.5 HN O.NNH nnH I NHH N I n.oH oo o.OOH 0NH I N0 N I I I I I O 5H\nO n
I I I 0.00H I H I I I I I O I I I I I O oH\mO 5
nNH I OOH O.o n5 5IOHH OOH I O5 On oOH I o0 o.o Nn H.OO HOH I O5 on I I I I I O HH\0O HH
oHH I 0O O.o 0o O.mOH 5OH I on O5 ONH I NO 0.5 O5 H.oOH O5H I O5 ON I I I I I O HH\mO OH
NHH I o0 H.o 5n N.OO OON I Oo NN I I I I I O I I I I I O OH\mO NH
50H I ONH 0.0 H5 0.0nH NON I O5 oH OoH I 5O n.NH NO O.NNH mOH I no oH I I I I I O oome o
OHH I NOH o.n H5 N.OOH 5OH I 5o OO nOH I 05 H.o 0o o.OO NOH I 5o Hn I I I n.5m I H nO\nO OH
NoH I ooH O.n Nn o.onH O0H I 5HH 5H O5H I ONH 5.0 no o.OoH o5H I HNH m I I I I I O oNxoO N
I I I O.NnH I H I I I I I O I I I I I O 0N\oO n
I I I O.NON I H I I I I I O I I I O.o0 I H nN\oO N
OoH I nO O.HH H5 0.HNH ooH I On O I I I I I O I I I I I O ON\oO n
anH I OHH n.5 Hm 5.mnH H5H I 5o NH NoH I oo O.HH Ho O.HHH 5NH I N0 n I I I I I O OonO 0
I I I I I O I I I I I O I I I o.Ho I H onoO n
Inalalnlol 4.010. an i Jaded—II NI 3 fl mm |% IIoImwdeI 0| 3| .0. mg I% IIoaeimIl ml 3 a
n HNHO _ — N fluHm _ _ H nuH0 _

.ooeHo owns xoosHso coo3uon ououuHo ouHo
noun ouos3 ooHOEeo ooosu ooueonosn axon oHom .omOH .ceOHnonz oxen snouoeo scum cOEHeo xoocnno

no ooooeHo oeno oounu on» On coasocoo Aoocnnaoo noncomo HHev sonw Mona mo oonuonueuo suuson .m oHnea

37

nHH I0OH o.H O0 o.OHH OnN InH H00 nO I50 O.H 00 OIOO nHN ION on0 O5 I00 O.H N5 H.N5 OON ION Noo H6008

I I I I I O I I I I I O H5 I Oo n.H 5 o.Oo O5 I oo 5 ONxOH OH
I I I I I O N5 I 5o N.o O5 n.OO O5H I On Nn 0O I HO O.H Hn O.oO NO I On O5 HH\OH OH
I I I I I O HOH I O0 o.o ON n.OO NHH I oo OH OO I 5o o.N OH 5.NO 00 I ON nH OH\OH OH
I I I I I O I I I I I O I N.n O 0.00 OOH I HO N 0N\OO nH
I I I I I O On I On 0.0 O 0.0n On I On 5H I I I I I O 0N\OO NH
I I I I I O 5OH I 5o H.nH n0 n.55 NOH I Ho OH I I I O.NOH I H 5N\OO NH
00 I NO O.o 0O H.oo OoH I on ON OO I Oo n.N nN O.oO nO I On ON O0 I Nn O.NH O5 o.oo OnH I 5N O 5N\OO HH
I I I I I O o0 I oo 5.o oo 0.n5 OnH I oo NN 0O I Ho 0.0 OO n.O5 OnH I oo NH HNxOO o

I 0.0 oN O.noH oOH I NnH N nOH I oo 0.NH 0o n.n5 OoH I Oo 5 I I I 0.05 I H ON\OO 0

I I I n.5O I H I I I I I O I I I I I O OHxOO O

N5 I HO O.n no O.oo nON I ON oHH 00 I DO O.N Nn O.No NHH I oo Ho no I 5n O.H ON H.Ho O5 I 5n oN onOO OH
NNH I N5 O.HH No O.5O OnH I no 0 nNH I oOH n.o No n.oHH OOH I On NO oNH I oOH n.O No O.oHH 5oH I o5 oH onOO OH
oOH I ON N.HN O0 5.NO ooH I On o I I I I I O I I I O.NOH I H onOO O
00 I HH 5.0 on O.oo O5 I On n nO I 5N 5.0 oo 0.0n nOH I ON NH I I I I I O OOxOO oH
O5H I NHH O.NH n0 5.0oH nOH I no HH 5OH I ONH n.O OOH o.0nH OOH I Nn Nn H5H I nHH O.NH 50 0.HoH OON I On NH OO\OO nH
oO I Oo 5.0H H5 o.Oo HOH I No HH no I NO 5.N 0N o.5O HHH I oo nN OO I No 5.o oo 0.05 ooH I on ON 50\OO o
I I I 0.0NH I H 5o I Oo O.H on H.no OOH I Nn nOH O5 I OO 0.0 oo O.oo oOH I Hn On oO\OO n
I I I I I O I I I O.noH I H OO I Oo H.5 OO 5.n0 onH I Ho OH On\OO N
nOH I nOH 0.0H oO 5.5oH nOH I NO o O5H I OnH 5.0 OO n.NOH NOH I OO 0 NNH I n5 5.0H NO O.5O NNH I oo o oN\OO nH
OoH I ONH O.o no O.onH oHN I o5 No OnH I NO N.OH 0o 5IOHH noH I Oo HH Oo I nn 5.H oN 5.00 OO I 5N 0o oN\0O NH
OOH I OnH n.O nn n.5oH 05H I ONH OH OOH I ONH H.5 ON 5.ooH nOH I ONH o OHH I OH o.HN OOH O.oo OOH I ON o nN\0O nH
oNH I OOH o.n 0o o.OHH OON I no OO OOH I ONH o.o O5 0.HoH HON I o0 on noH I 05 H.oH OO O.oHH OoH I Oo O NNxOO HH

 

oHH I noH T... o... «63 :H I so He HnH I S 93 «o H.oHH nHN I 3 3 Ho I H. n.n no o.oo OH I on «H :30 0

3H I 9.3 v... «S n.H...H can I 3 no nnH I 2: H.» 2. n.nHH 3H I cm «a I I I 92: I H 33° 3
I I I n.nou I H I I I I I o I I I I I o 33¢ a

on I an a... 3 o.o... Ha. I H... H vs I «H. n.n 2. o.n. onH I 3 He onH I an o.o ov «.2: 2H I on HH 323 n

I I I I I o I n.n" 2. 0.5H 2H I 2: u ooH I 3 n.n nH n.oo noH I on o nHBo s

3H I 2. H.nH 2. H.3H .3 I 3 e I I I I I o I I I I I o onoo 3
I I o.H.H an o.~HH 3H I: H oNH I2. H...” 3 o.HoH oHH Ina n I «.a ca 992 onH IuHH « 230 v

2H I no o.o S H.ooH onH I S OH nHH I 3 o.o en SSH 3H I on v I I I I I o 83° 3
I I I I I o 3 I 3 T... «H o.HH. 3 I Ho n I I I I I o 830 v

noH I «3 nn. H. n.o: «H I .3 o HNH I an n.n 3 o.oHH 3H I HH. 3 3H I 2 n.NH Ho «.2: onH I an S 330 n

nHH I so n... 2.. «.2: 2: I no I I «.3 a... H.ooH NHH I on m .3 I on «.1 Hm n.ooH nnH I 1. n 3:3 3
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39

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44
frequency, absolute amount, and proportion of bloater in the diet
decreased with increasing predator size in both basins. While the
proportion of bloater in the diet was significantly greater in the south
than in the north, this was due primarily to the lesser amount of
alewife in the diet in the south and not to a greater amount of bloater.
Frequency of occurrence of bloater in the diet was slightly greater in
the south from July on, but the number and biomass consumed did not
differ significantly between the two regions.

Rainbow smelt occurred in the diet periodically from April through
July as adults and then consistently from August on as both adults and
YOY. Sizes consumed ranged from 20-240 mm and like alewife, were
representative of sizes typically found in the lake. The frequency,
absolute amount, and proportion of rainbow smelt in the diet were
consistent among predator size class, and were much greater in the north
than the south.

Yellow perch rarely occurred in the diet in the north, but occurred
periodically in the south in all months as small adults less than 170
mm, and in the fall primarily as juveniles 40-80 mm in length. In the
south, the frequency, absolute amount, and proportion of yellow perch in
the diet appeared consistent between predator size class, and were equal
to or greater than the contribution of smelt.

Other species of fish occurred only occasionally in the diets and,
overall, contributed very little. Of these, nine-spine stickleback
(ggngigigg pungitius )occurred most often, and primarily in chinook
caught near the Manitou Islands. Of some interest was the occurrence in
the diet of several species of fish that are not typical inhabitants of

Lake nichigan waters such as northern pike (559; lggigg) and bluegill

45

(Lgpgmig macrochigus). Heavy rains in September of 1986 led to a 100-
year flood event that washed out local dams and caused extreme discharge
from area rivers. Coincident occurrence in the chinook diets of these
typically riverine fish indicated that many of the fish species
associated with these rivers were flushed into Lake Michigan and that
the chinook were opportunistic in their predation on them.

Invertebrates occurred periodically through the year with some
apparent seasonal trends. The amphipod Dipggeia gpp; appeared to be the
most important aquatic invertebrate for these chinook, although paphgia
g2; and flygig relictg were also found. Although less frequently,
terrestrial insects were also consumed, occasionally in large numbers.
These aquatic and terrestrial invertebrates occurred primarily earlier
in the season and contributed more to the diet of smaller chinook, where
they were occasionally the predominant prey item (Figure 10a). The
large exotic cladoceran, Bythotrephes cedggstroem , which appeared in
Lake Michigan in the summer of 1986 (Lehman 1991), was first observed in
the chinook diets on July 18, 1986. From then on it was the only
zooplankton that occurred in the diet and remained common through the
fall. Although gythotrephes were found in chinook of all sizes, it
occurred more frequently and in greater numbers in the diet of smaller
chinook, and more frequently in chinook from the northern basin.
Overall, invertebrates contributed only a small portion to the diet,
primarily occurring in smaller chinook, particularly in the spring.

Of some concern may be the occurrence in the stomachs of chinook of
other items associated with human litter such as plastic food wrappers
and cigarettes. Such items were more common in the stomachs of

steelhead (data not presented here), which typically feed near the

46

surface and in association with scum or trash lines where this material

may collect.

Digested State of Prey

There was little diversity in the observed contents of individual
chinook stomachs. Although several prey types typically characterized
the diet of all chinook on a given day at one location, most fish had
just one prey type in their stomachs. When more than one were present,
the digested state of the prey often indicated the two types had been
consumed at different times. The occurrence of multiple prey types
appeared similar for all size classes of chinook, though was more common
in summer and fall than in spring.

The digestion state of the four major forage fish showed similar
distribution patterns, although each differed significantly from one
another (p < 0.05)(Figure 18). For all species, most were 50% to 75%
digested, with only a small percent appearing to have been ingested
shortly before the chinook was caught. Yellow perch and rainbow smelt
tended to be less digested than alewife or bloater.

On four dates, enough chinook were collected from catches in both the
morning and the afternoon of the same day at one location so that
comparisons of diet between morning and afternoon caught chinook could
be made. In each case, the diet was different between morning and
afternoon, but in no consistent manner that indicated anything other
than the usual random variation typically observed between fish.
However, alewife and bloater in the stomachs of chinook caught in the
afternoon were somewhat less digested than in chinook caught in the

morning (Figure 19). Days when samples were collected in both morning

47

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Figure 18. States of digestion observed for alewife, bloater, smelt,
and perch consumed by chinook salmon from eastern Lake
Michigan, 1986.

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States of digestion observed for alewife and bloater
consumed by chinook collected in the morning and in the
afternoon from eastern Lake Michigan, 1986.

 

 

49

and afternoon from one location were limited and did not include enough
perch or smelt for similar comparisons. When all morning and all
afternoon samples were combined (regardless of date or location), no
differences were apparent, indicating that the variation from day to day
and from location to location was greater that any diel differences that
may exist. There was no observed difference in the digested state of

prey between basins or among seasons.

8 f Consume

Seasonal trends in size of prey consumed by chinook showed marked
similarities between 1986 (Figure 12) and 1985 (Figure 13), indicating
patterns observed are likely typical of annual forage use. Chinook
consumed alewife and smelt of all sizes available in Lake Michigan, but
rarely consumed adult bloater or perch over 160 mm in length, despite
their recent increased abundance in the lake. In both years, large
adult alewife were commonly consumed in April through May and August
through early September, but were less frequently consumed in June and
early July. Sizes of bloater, smelt, and perch in the diet were
consistent from April through mid-August, a period when only adult prey
(including yearling alewife) were consumed. But from mid-August through
October, YOY alewife, bloater, and smelt, as well as juvenile perch were
the primary diet.

Similarity in the sizes of bloater, smelt, and perch consumed by
predators from both the northern and southern basin of eastern Lake
Michigan indicate their size composition was similar regardless of

region. Sizes of alewife consumed from April through July, however,

50

indicated that yearling alewife (50-120 mm) were a much smaller
proportion of the diet in the south than the north (Figures 18 and 19).

Of all alewife consumed by chinook in 1986, 33% were young-of-the-
year consumed in from September through October (Figure 17). In 1985,
bloater, rather than alewife were the dominant YOY fish consumed by
chinook (Figure 13). Heavy consumption of primarily YOY fish in the
fall was also observed for coho and steelhead (Figures 15 and 16) and
for both accounted for the majority of fish found in their diet. From
May 1 through August 15, lake trout ate primarily alewife, followed by
smelt, bloater, and perch. Like chinook, they ate all sizes of alewife
and smelt available, and consumed few bloaters and perch larger than 160
mm (Figure 16). Closure of the lake trout season on August 15 precluded
determination of their fall diet using sport caught fish.

There was little evidence that larger chinook regularly ate larger
individuals of a particular prey type (Tables 2-4). There was no
difference in the sizes of alewife, bloater or smelt consumed for 44 of
50 paired comparisons (p < 0.05). Only three of the paired comparisons
indicated larger chinook had consumed larger alewife, and three
comparisons indicated larger chinook had consumed larger smelt. Larger
individuals of both these prey types provided more opportunity for
selection differences to exist than for bloaters. In each case, the
magnitude of these differences was small compared to differences in size
of each prey type consumed between dates and over time.

Because of the increase in predation on alewife by the larger size
classes of chinook, particularly in the spring, and the larger average
size of alewife consumed relative to bloater, differences in prey size

consumed by different size chinook were more common when size of all

 

51

prey types were combined (Table 5). Larger chinook consumed larger
prey fish in 17 of 65 paired comparisons, while smaller chinook consumed
significantly larger fish for 3 of the 65 comparisons (p < 0.05).

Still, for the majority of samples, there was no difference in the sizes
of prey fish consumed by different size chinook. Overall, predator size
(over the range of sizes examined) seemed of lesser importance in
determining sizes of prey consumed than availability of certain size

prey at a given location and time.

Qomparisons of Apparent Rations

Based on the observed quantities of stomach contents, Chinook from
the northern basin of eastern Lake Michigan apparently consumed roughly
twice the number and twice the biomass of prey (apparent ration)
compared to chinook from the southern basin. This difference was
consistent throughout the season and across all predator size classes
(Figures 8a, 8b, 9, 10a, 10b, and 11). Within each basin, differences
in the amount of prey consumed by the different size classes of chinook
were evident, but only in the spring. Through May in the south and
through June in the north, size-3 chinook had apparently consumed
roughly twice the number and biomass of prey compared to size-2 chinook.
Size-1 chinook apparently consumed very little during this period. From
June on in the south, and July on in the north, there was very little
difference in the amount and type of prey found in the stomachs of
different size chinook from the same basin.

The greater apparent rations of larger chinook were not in proportion
to their greater size. When adjusted for predator weight (grams of prey

per kg of predator), size-l chinook from both basins and size-2 chinook

52

from the north had the largest adjusted rations (O.50-0.62% body
weight), and size-2 chinook in the south and size-3 chinook in both
basins had smaller adjusted rations (O.lB-O.30% body weight)(Figure 20).
Similarly, size-2 chinook from the south and size-3 chinook from both
basins had a significantly greater proportion with empty stomachs than
did size-1 chinook from both basins and size-2 chinook from the north
(Figures 6a, 6b, and 7)(p < 0.05).

Seasonally, both apparent ration and frequency of stomachs containing
food were highest in the fall for all sizes of chinook from both basins
and coincided with the predominance of Y0! fish in the diet. Ration and
frequency of feeding were also high for size-2 and size-3 chinook in the
spring, when they feed primarily on alewife. Apparent ration and
frequency of stomachs with food were the lowest for size-2 and size-3
chinook in July when the occurrence and amount of alewife in the diet
was low. For size-l chinook, apparent ration and frequency of stomachs
with food were lowest in the spring when few were feeding on fish. Once
bloater began to occur in their diet in June (in the south) and July (in
the north), apparent ration and frequency of stomachs with food

increased to and remained at high levels through the rest of the season.

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DISCUSSION

The sampling of 9,427 salmonines over four successive years: 1,513 in
1983 and 2,705 in 1984 by Kogge (1985); 1,578 in 1985 by Nurse (1986);
and 3,631 from the fall of 1985 through 1986 reported here, represent
one of the largest collections of data describing the diet of Lake

Michigan salmonines.

W

Bloater appear to have been a consistently important portion of the
diet of eastern Lake Michigan chinook salmon from at least 1984 through
1992. Results from Kogge (1985), Nurse (1986), and Rybicki (1993)
indicate bloater to be a major if not dominant component of the diet,
ranging from 21-30% in the south to 5-26% in the north and from 39-83%
for small (age 1) to 11-29% for large chinook. However, throughout this
same period alewife, despite their reduced abundance, have remained a

predominate forage, particularly for larger fish.

WW

Substantial changes in prey type consumed both from day to day and
over the season indicate Lake Michigan salmonines are apparently capable
of quickly switching among alternate prey types (Ware 1971, Murdoch et.
al 1975), and are capable of feeding on whatever prey happens to be most

available and most easily caught.

54

55

Following the decline in consumption of large adult alewife from
relatively high levels in the spring to low levels in June (south) and
July (north), consumption of other prey species increased (Figures 6a
and 6b). A similar summer decline in overall apparent ration and a
shift to other species was noted by Jude et al. (1987) for fish
collected from 1973-1982 in southeastern Lake Michigan, a period when
alewife were generally more abundant. The movement of mature alewife
into shallow nearshore waters to spawn may limit their availability as
prey during this summer period. By August, after most alewife have
finished spawning, large alewife were again more common in the diet
(Figure 15). Along with the continued consumption of other species,
alewife accounted for an increase in apparent ration over that of the
mid-summer lows.

The abrupt switch from predation on adult prey fish in August to YOY
fish in September was likely prompted by the breakdown in thermal
stratification that through summer had provided both the preferred
warmer epilimnetic habitat for YOY fish (Brandt et al. 1980) and
isolation from predation by the typically cold water salmonines. At
this same time, YO! fish likely were reaching sizes at which they begin
to move into deeper, cooler waters, making them more available as prey.
In experimental feeding studies (Savitz and Bardygula 1989), prey fish
that remained near the surface were rarely attacked, but were readily
attacked when suspended in the water column. Savits and Bardygula
(1989) also noted that adult alewife were more difficult to capture than
small alewife because of faster escape swimming speeds and their ability

to turn very sharply when attacked. Slower swimming speeds of YOY

56

alewife and their inexperience with predator attacks likely contribute
to their easy capture and thus dominance in the fall diet.

The near cessation of adult alewife consumption by chinook in the
fall in lieu of 20! fish indicates Lake Michigan salmonines may exhibit
the theoretical tendency to feed disproportionately on the most
available prey (Ware 1972). It may also indicate that the abundance and
ease of capture of Y0! fish is sufficient to meet predator consumption
demands in the fall.

The establishment of search images (Wars 1971) has also been
associated with such disproportionate predation. YOY fish, primarily
alewife, are typically the first fish heavily preyed upon by juvenile
chinook (Elliott 1993). Formation during this time of a restricted
search image may increase the tendency for adult chinook to pursue YOY
fish when they become available in late summer and fall.

Vulnerability of adult alewife to capture may also vary seasonally
with changes in their energy content and condition. In Lake Michigan,
the energy content of adult alewives is highest in the fall and lowest
in the spring (Flath and Diana 1985, Strange and Pelton 1986). Adult
alewife often experience die-offs during the spring period when their
energy reserves are low and condition is poor. These factors may also
act to impair the ability of alewife to evade predators, increasing
their vulnerability in the spring -- a period when many are consumed.
Higher energy reserves in the fall may help adult alewife better evade
predators and contribute to a greater disparity in vulnerability between

adult and YO! alewife.

57

WW

Variation in the size of prey consumed by different size predators
appears largely dependent on periodic and seasonal differences in prey
availability. Although some evidence for size selective predation was
observed (Table 4), differences were minor in comparison to seasonal
effects.

Predator size is often positively correlated with prey size in
systems where relative density of large prey is high (so that gape size
rather than prey availability limits maximum size of prey consumption -
see Daan (1987) for example of ocean cod population). In Lake Michigan,
the dominance of smaller prey and the scarcity of prey items large
enough to avoid predation precludes the occurrence of strongly positive
predator prey length relations. The capability of these large predators
to eat much larger prey is evidenced by the rare observation of a 300 mm
chinook salmon found in the stomach of a 70 cm (3.6 kg) lake trout
(Denny Grinold 1989, photographed data). In Lake Superior where lake
herring provide an abundant large prey item, lake trout commonly consume
individuals in excess of 300 mm in length (Conner et al. 1993).

Earlier surveys of southern Lake Michigan salmonines (Jude et al.
1987) and of Lake Ontario salmonines (Brandt 1986) did document much
stronger positive correlations between predator and alewife size. At
the time of both studies, abundance of large adult alewife was high and
may have provided a greater likelihood of size dependent predation.

Jude et al. (1987) also reported seasonal differences in size of alewife
consumed for the years of 1973-1982 that were very similar to those
observed in this study (Figures 13 and 14). It appears that seasonal

differences in abundance and availability of different size prey may

58

have always been more important determinants in forage use than size
selective tendencies, even during periods of high adult alewife
abundance.

The greatest indication of size dependent predation observed in this
study was the tendency of smaller chinook to have consumed more juvenile
bloaters and less large alewife than larger chinook. Further support
was the greater occurrence of differences in average prey size between
the different size chinook when all prey types were combined. This
follows the generally excepted premises of optimal foraging theory
(Werner and Hall 1974). During this study, chinook 50 cm or greater in
length consumed maximum sizes of all prey types while during the
previous decade chinook had to reach lengths of 60 to 70 cm to do the
same. The difference is again related to a greater abundance of larger
alewife during the 19703.

It should be noted that much stronger positive correlations between
predator and prey length can also be shown for these data if the
dependence of prey size on season is ignored. However, because smaller
chinook only fed heavily on alewife in the fall when mostly 20! fish
were consumed (by all size chinook), these correlations are artifacts of

the seasonal differences in prey use by different size chinook.

Bglgpipp pf Diet to Forage Abundance and Distribution

An apparently disproportionate reliance on alewife by chinook despite
the lakewide decrease in alewife abundance has been interpreted by many
to indicate a preference for adult alewife by chinook (Stewart and

Ibarra 1991). This interpretation may not be appropriate. Because only

59

bloater less than 160 mm in length were consumed by chinook salmon, most
of the adult portion of the bloater forage biomass was not utilized.

In recent years, Stewart and Ibarra (1991), Brandt et al. (1991),
Crowder and Crawford (1984), and Eck and Brown (1991), have all
concluded that much of the bloater biomass is of large adults that are
too deeply distributed, and occupy water too cold, for effective
predation by the exotic salmonines. In contrast, adult alewife prefer
the same temperatures and thus occupy the same habitat as salmon (Brandt
et. al. 1980), making them more available for predation. Juvenile
bloaters, which remain spatially segregated from the adult bloaters by
inhabiting pelagic waters (Crowder and Magnuson 1982, Brandt et a1
1991, Crowder and Crawford 1984) are also available as prey for pelagic
predators.

For 1990, Eck and Brown (1991) estimated that of the 300,000 metric
tones of bloater in Lake Michigan (estimated from fall forage surveys
using bottom trawls), only 30,000 mt, or 10%, were of sizes typically
consumed by salmon. This compares an estimated 42,000 mt of alewife
present that same year, and an estimated 17,000-51,000 mt of alewife
present since 1981 (Brown et al 1993). Thus, alewife may still be more
available as forage than bloater, despite the predominance of bloater in
the lake.

The pelagic nature of alewife and benthic nature of adult chub
indicate abundance estimates using bottom trawls may not be
representative of total prey availability, although trawls do provide a
meaningful index of year to year forage abundance (Eck and Brown 1985).
Hydroacoustic methods of forage assessment have indicated alewife,

particularly those less than 120 mm, may account for a much larger

60

proportion of the forage biomass than has been indicated by bottom
trawls. Large adult alewife are known to be more deeply distributed
during the day than smaller alewife (Brandt 1980). While all alewife,
juvenile bloater, and smelt exhibit vertical migration at night (Janssen
and Brandt 1980), moving into the pelagic environment, adult bloaters
apparently remain near the bottom (Brandt et al. 1980). Although
hydroacoustic techniques may lead to an underestimate of the more
benthic oriented forage, the estimated higher proportion of smaller fish
more closely matches prey composition of salmonine diets, and thus may
more closely reflect forage used by pelagic predators.

The reduced alewife abundance observed for 1983-1985 (US Fish and
Wildlife Service (USFWS) forage assessment surveys) spurred a great deal
of concern about the adequateness of an apparently depleted supply of
forage. It is quite possible that because of increases in juvenile
bloater abundance and a greater than estimated abundance of Y0! fish,
forage available to salmon did not decline nearly as precipitously as

was perceived from bottom trawl surveys.

Agppgg-lakg Differences in Diet

The major presence of bloater in the diet of eastern Lake Michigan
chinook is in marked contrast to the apparent lack of bloater in the
diets reported for angled chinook from western Lake Michigan. In 1982
and 1983 (Hagar 1984) and in 1990-1993 (Toneys 1992, Peeters 1993),
bloater accounted for less than 0.6-2.5% of the diet of chinook from
western waters. Of species other than alewife, rainbow smelt was the
most common. Although the occurrence of smelt in diets of predators

from western Lake Michigan can at times be considerable (Stewart and

61

Ibarra 1991) and comparable to proportions of prey species other than
alewife from eastern Lake Michigan chinook, alewife appear to have
generally accounted for a greater proportion of the diet of chinook from
western waters than from eastern waters of Lake Michigan over the past
decade.

Regional differences in diet are compatible with the apparent spatial
distribution of alewife, bloater, smelt, and perch in Lake Michigan.
Hydroacoustic measures of planktivore abundance in 1987 (Brandt et al.
1991) indicated that forage abundance and distribution varied
seasonally. In 1987, and generally in most years since the decline of
alewife and recovery of bloater, alewife and smelt have been more
abundant and made up greater proportions of forage in the northern and
western regions of the lake. Bloater have been fairly abundant
throughout the lake but are more dominate in eastern waters. Perch have
been more abundant in the southern regions of the lake (Gary Eck and Ed
Brown, USFWS, personal communication).

Thus, seasonal and regional differences in the characteristics of the
diet of chinook seem to follow trends in the complementary use of
habitat by predators and prey. Diet, therefore, may best be explained
as a reflection of prey vulnerability and availability. This would
indicate that Lake Michigan salmonines might be better characterized as
being highly opportunistic feeders within their habitat. Description of
their behavior as being selective is only an indication of our
incomplete understanding of their seasonally changing interactions with

a dynamic prey base.

62

WW

Several trends in diet observed in this study support observations
reported for other years and regions. The increase in the prOportion of
alewife in the diet with increasing predator size, and the increase in
proportion of species other than alewife through the season has been
reported for nearly all diet studies in Lake Michigan since the late
1970s. In general these trends have been most pronounced in areas where
and during times when alewife abundance was the lowest. For example,
the seasonal increase in the proportion of other species in the chinook
diet began in June in the southeastern basin, in July in the
northeastern basin, and finally in August and September along the
western side of Lake Michigan. Similarly, species other than alewife
contributed the most to the diets of chinook from the southern basin of
eastern Lake Michigan, less to chinook from the northern basin, and
least to chinook from western Lake Michigan. The increase in the amount
of forage consumed in September and October for eastern Lake Michigan
chinook may also occur elsewhere, but few data have been reported for
late fall for western Lake Michigan.

Prior to the alewife decline, and again in recent years for areas
where alewife are most abundant, other species contribute less to the
diet of chinook salmon (Jude et.al. 1987, Hagar 1984, Toneys 1992,
Peeters 1993) than they did during periods of lowest alewife abundance
(Stewart and Ibarra 1991, Kogge 1985, McComish 1989, data presented
here). Again, increases in the proportion of species other than alewife

does not necessarily indicate their increased consumption.

63

W

The potential for forage limitation in a system where predator
abundance is not directly governed by food availability but is largely
controlled by stocking, has been a major concern. Evidence for reduced
forage availability, and thus consumption, has hinged on observed
differences in growth of predators, changes in the abundance and
composition of forage stocks, and subsequent changes (or lack of change)
in diet composition -- all integrated through the bioenergetics analysis
of predator demands. A more direct measure of changes in forage
availability would be possible if some measure of stomach fullness
(apparent ration, amount of prey per stomach) were compared for
homogeneous groups of predators from different times and different
regions of the lake.

The reduced amount of alewife in the diet of chinook in the southern
basin observed here, and particularly, the relative lack of yearling
alewife compared to the northern basin, appears to indicate that rations
may have been limited for chinook in southeastern Lake Michigan in 1986.
How long this may have been the case is difficult to judge. Few of the
earlier diet studies have reported actual amounts of consumption. Those
that have (Jude et al. 1987) are difficult to compare because of
differing methods of collection and small sample size.

The most revealing comparison of apparent rations may be between this
data and data collected in 1991 and 1992 for angler-caught chinook from
Wisconsin waters of western Lake Michigan (Toneys 1992). Despite the
poor survival of chinook since 1988, many of those now caught are much
larger than those caught in 1986 and average size at age of chinook

since 1988 appears to have increased (Smith 1993, M. Toneys, Wisconsin

64

DNR, personal communication). It might therefor be expected that
chinook in more recent years may be consuming more prey than in earlier
years. However, the diet data from Wisconsin waters indicate the
average amount of prey consumed by chinook from both northern and
southern waters of western Lake Michigan may be similar now to what it
was for chinook from the northern waters of eastern Lake Michigan in
1986 (Figure 21). This evidence may support a hypothesis that lakewide
forage abundance was not, and is not now, strongly limiting chinook
growth, at least in the northern and western regions of Lake Michigan.

Forage availability, however, may have been limiting in the
southeastern region of the Lake in 1986 compared to elsewhere, and could
have contributed to reduced growth for chinook that spent extended time
there. Whether this is still the case is not known. Possible forage
limitation in the southeastern region of the Lake may have occurred for
some time prior to 1986. Jude and Tesar (1985) reported a 84% decline in
adult alewife abundance in the near-shore region of southeastern Lake
Michigan from 1974-1977 after which alewife remained at low levels.
This localized reduction in alewife was four years earlier than the
largest lakewide decline of adult alewife observed for 1981-83. If
greater production of alewife occurs in the northern basin of Lake
Michigan, and particularly in Green Bay, the southeastern portion of
Lake Michigan might be expected to show earlier declines in alewife

abundance.

ggowtn gpg Condition

A reduction in ration of approximately 50%, as might be indicated

here for fish residing in the southeastern waters of Lake Michigan,

65

Northern Basin Southern Basin

Size 3

 

 

   

 

 

7?
9 Sist
2
£6
E 3 , ’\
z
i
8
s
a.
Size1

3800333888345‘30u338888

15

    

10

 

   

ll {FM

 

 

 

Michigan Waters _ _ ._ Wisconsin Waters Wisconsin Waters
1 986 1 990 1 991

 

 

 

 

Figure 21. A.comparison of the amount of prey consumed by chinook
salmon from the eastern and western waters of Lake Michigan.
Wisconsin waters values are based on reconstructed biomass
data from Toneys (1992) but have been adjusted to reflect
actual biomass per stomach. This adjustment is based on the
average proportion of the reconstructed biomass that was
observed in the stomach as actual biomass in 1986.

66

might theoretically result in poorer condition or slower growth for fish
that spend an extended period of time in the southeastern part of the
lake. Typical measures of condition that rely on various forms of the
length-weight relation (Anderson and Gutreuter 1983) may not work well
for chinook salmon. Chinook have the ability to replace depleted fat
reserves with water, thus maintaining the same length-weight
relationship despite differences in physiological condition. A more
detailed analysis of health and condition that includes measures of
lipid and water content might be more appropriate indicators of true
condition or well-being.

In recent years, the discovery that annular growth rings do not
appear to form on chinook scales until mid-summer (D. Anson and S.
Lazar, MDNR, personal communication) has caused a modification in the
methods used by MDNR to determine age of chinook since 1985,
particularly for mature fish. Back calculations of size at annular
formation and apparent growth since formation observed on chinook scales
collected during this study confirm these findings, and also indicate
that the time of annulus formation may be quite variable. For some
fish, recently formed annular rings were apparent in early spring, while
others were not apparent until late-summer.

These findings might be consistent with differences in lipid and
water content of chinook in the spring. If chinook come out of winter
with expended energy reserves, much of their spring consumption may go
into rebuilding these reserves. The initiation of post-winter somatic
growth, during which annulus formation becomes apparent, may not be

realized until later in the spring or summer after fat reserves have

67

been rebuilt. Differences in regional forage availability could
therefore contribute to variation in the time of annulus formation.

The ability to determine growth of Lake Michigan chinook has been a
constant topic of debate. It has been inferred from changes in average
size of chinook in the sport catch, that growth of chinook has changed.
Although Hansen (1986) did observe declines in average size of sport
caught chinook from western Lake Michigan waters as well as a general
decline in trophy weight and condition, he could not, using a more
complete data set, support the assertions by Hagar (1984) and Stewart
and Ibarra (1991) that growth had declined.

Confounding variables have to date likely precluded an accurate and
acceptable measure of chinook growth. These include increasing
population size driven by stocking and increasing fishing pressure and
harvest characteristic of the pre-1987 fishery; decreasing population
size and decreasing fishing pressure and harvest characteristic of the
post-1987 fishery; potential inaccuracies in aging of fish with scales;
and variation in recruitment of natural fish (Elliott 1993, Zafft 1992).
Further investigation of the effect that changing fishing pressure and
harvest can have on the size structure of the chinook population is
needed. For example, declines in fishing effort, and particularly
declines in the targeting of chinook since 1987, could be a factor in
the apparent increase in size observed in recent years. Accurate
determination of growth trends and of growth increments for Lake
Michigan chinook will necessitate the comparison of size at age (both
actual and back calculated) of known age and known source (hatchery and
natural) fish from the sport fishery, from assessment netting, and from

fish returning to rivers.

68

WW

Catch rates and harvest of chinook from Lake Michigan seem to mirror
both the regional and seasonal differences in apparent ration (Figure
22). In eastern Lake Michigan, lowest catch per unit effort (CPE) for
chinook typically occurs in March and then later in June (Rakoczy 1986,
1992) coincident with lowest observed apparent rations. Highest CPE
typically occurs in late spring and in the fall coincident with higher
apparent rations. In western Lake Michigan, chinook are rarely caught
before June (Brad Eggold, WDNR creel data). Beginning in June, CPE for
chinook quickly reaches high levels where it remains through August,
after which CPE declines into the fall. This difference in the seasonal
trends of CPE between the eastern and western waters of Lake Michigan
may indicate a movement of chinook from eastern waters into western
waters in June, and then back again in the fall.

As they are in the marine environment, Great Lakes chinook, coho, and
steelhead appear to be highly mobile through all life stages (Keller
1993, Elliott 1993, Terry Lychwick, WDNR, Rakoczy, MDNR, Hess, IDOC,
personal communication). Preliminary results from returns of coded wire
tagged salmon (Keller 1993) seem to confirm a general migration pattern
of chinook in Lake Michigan that takes much of the population away from
southeastern Lake Michigan through mid summer. It seems probable that
although chinook are present in the southern basin, residence there for
any one individual may be short term. Because they may be able to move
from areas of low prey availability to areas of the lake where forage,
particularly alewife, are more abundant, they may not exhibit reduced
growth or condition to the degree that would be expected if reduced

rations were persistent. Such movement would also indicate that seasonal

0.20 r-
o,1a — Eastern Lake Michigan
0.16 -
0.14 -
0.12 h
0.10 -
o.oa — North-1986

0.06 -

0°04 “ South-1986
(102 r

CPEforBoatflshery (fish/hour)

 

 

0.45 -
0.4 " Eastern Lake Michigan

/\

I

0.3
0.25
0.2
0.1 5
0.1
0.05 -

I I

I

1985
1987
1986

I

 

 

0.4 —
0.35 -
0.3 '-
0.25 I-
0.2 -
0.15 r
0.1 _
0.05 -

Western Lake Michigan

CPE for Charter Fishery (fish/hour)

 

 

 

o V T U I
' I ‘ I
apnl may lune luIy aug se pt oct

Figure 22. Monthly catch rates estimated for chinook salmon from
eastern and western waters of Lake Michigan, 1986 (data
from Michigan and Wisconsin DNR creel census programs).

70

averages of diet may not be representative of the lake population.
Actual seasonal average data will need to include the combination of all
regions diet, known CPE, and perceived movement data.

Lake trout have been characterized as having slower growth in the
southern basin compared to the northern basin of Lake Michigan (Rybicki
et al. 1990, Eck and Wells 1983). Although lake trout can be fairly
migratory, as a population they typically have a relatively small home
range compared to pacific salmon, and commonly remained in the vicinity
of their stocking site (Holey and Miller 1992, Rybicki 1990). Lake
trout may, therefore, be more affected by localized forage abundance
than salmon. Since habitat typically occupied by more near-shore
populations of lake trout overlaps strongly with adult alewife and
alewife have been the dominant forage of near-shore lake trout (Miller
and Holey 1992, Hogge 1985), reduced growth of these near-shore fish
appears to support the notion that alewife as forage is more limiting in

the southern basin than in the northern basin.

Qgg pf fiipgpgrgeticg Models

Continued heavy predation on alewife following their decline in the
early 1980s, has led several authors to the conclusion that the alewife
population is not capable of supporting the predatory demands of Lake
Michigan's stocked salmonines (Stewart and Ibarra 1991, Brandt et al.
1991). Much of this has been supported by bioenergetics assessments of
the predator-prey dynamics of Lake Michigan (Stewart et al. 1991,
Mitchell and Hewett 1987).

Empirical data presented here, however, differ somewhat from data

used in these bioenergetics assessments. First, most recent

71

bioenergetics models for Lake Michigan have assumed a lakewide diet of
adult fish reflective of angled fish sampled from May through August
from western Lake Michigan (Stewart and Ibarra 1981). Previously
described differences between the diets of chinook from eastern and
western Lake Michigan, and the substantial differences in diet
composition in the fall, particularly in the sizes of prey fish
consumed, indicate that use of more detailed diet data would be
beneficial in these model applications. Winter diet data collected in
1991-92 by Indiana DNR (D. Brazo, personal communication) and limited
data collected by Jude et al. (1987) indicate that chinook may feed very
little over winter —- unlike lake trout, which have been found to feed
on alewife throughout winter. During this study, the few chinook that
were collected in early April had consumed very little prey compared to
those sampled in late April and early May. Exposure of chinook to the
winter temperature regime of the Great Lakes may have a substantial
effect on their feeding and behavior.

Second, the models have also predicted consumption by salmonines to
be highest in late summer when water temperature is high and chinook are
large (Stewart 1991, Mitchell and Hewett 1987). Amount of prey consumed
by chinook collected in this study consistently indicated that rations
were the highest in September and October for all size chinook, and also
higher in the spring for the largest chinook. Warmer late summer water
temperatures should have had little effect on consumption since
temperatures occupied by feeding chinook were consistent from July
through October. Thermal stratification of the lake during summer may
isolate prey from predators. Typically water along the shore of eastern

Lake Michigan is more strongly stratified than along the western shore

72

(Mortimer 1975). Thermal habitat may, therefore, be more limiting for
chinook in the eastern waters than in western waters during summer.

Large alewife apparently have been the forage that has best provided
the large ration needed for large chinook to meet energetic demands.
With declines in the abundance of larger alewife, it has been expected
that chinook will have to rely more on smaller alewife. (Stewart and
Ibarra (1991) indicated that a shift in chinook diet from large alewife
to smaller alewife, combined with slower growth of chinook, would result
in a 20% decline in conversion efficiency. This would necessitate an
increase in daily rations to maintain net energy gain. The consumption
of small alewife by eastern Lake Michigan chinook appears to be
seasonally dependent. Further, in the fall when chinook diets were
dominated by YOY fish, apparent rations were greatest. Since forage
value of alewife is as much as 1.6 times greater in the fall than during
other times of the year (Flath and Diana 1985), this is likely the
period of greatest energy intake. While this energy intake could be
even greater if large alewife rather than small alewife were consumed,
the available data indicate that chinook have always consumed smaller
alewife in the fall than during other times of the year, even when large
alewife were very abundant.

If future bioenergetics assessments of predator-prey dynamics in Lake
Michigan are to be reasonably accurate, they will need to: determine
lake-wide estimates of consumption by integrating movement and CPE data
with regional diet data that encompasses the entire season; account for
seasonal differences in energy content of prey; account for seasonal and
size specific differences in the lipid and water content of chinook; and

most importantly, use unbiased measures of true growth.

73

zappigippipg Total Consumption

Because of the differences observed in the diet of different size
(and presumably different age) chinook, overall consumption of different
forage species by chinook in eastern Lake Michigan waters is dependent
on the size specific abundance of the chinook population. To present a
comparative index of total seasonal consumption (April-October) by all
cohorts of chinook, a simple model was developed (Figure 23). Annual
mortality rates from 20% to 80% were applied to age-1 recruits and then
diet, expressed as biomass of prey per age-1 recruits, was summed for
all surviving fish ages 0.1 through age 0.5.

To keep this process simple, mortality adjustments were made for each
age class prior to the season rather than during the season. Also, the
contents of chinook stomachs were assumed to reflect the type and amount
of food consumed so no adjustment for differences in digestion or
evacuation rates due to seasonal temperature changes, or due to
different prey types or predator sizes, was made. The first assumption
likely overemphasizes the fall diet when fishing mortality would reduce
the number of chinook. The second assumption likely overemphasizes the
spring diet when colder water temperatures would reduce consumption.
Because the nature of these biases counter each other, this method may
be a realistic approximation. Using mortality rates typically assumed
for chinook salmon in Lake Michigan (Stewart and Ibarra 1991, Eck and
Brown 1985, Mitchell 1987), the model indicates that only 25% of the
total seasonal consumption of forage by chinook in eastern Lake Michigan
would be attributed to age-3 and older chinook. Alewife would account
for roughly 30% (in the south) to 60% (in the north) of total prey

consumed (Figure 23).

74

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75

Despite the dominance of adult alewife in the diet of larger and
older chinook, total consumption of forage appears driven to a larger
extent by the more abundant age-1 and age-2 chinook, which in eastern
Lake Michigan rely very little on adult alewife. Since the reduced
abundance and shift in age structure of chinook salmon since the 1988
episodic mortality associated with bacterial kidney disease (Smith 1993,
Nelson and Hnath 1990), large alewife should have experienced a greater

decrease in consumption relative to smaller alewife and bloater.

W

Alewife recruitment is controlled by a number of biotic and abiotic
factors. The difficulty this marine species has with functioning
optimally in the cold Great Lakes environment has been well documented,
and is generally considered one of the major factors affecting alewife
abundance (Bergstedt and O'Gorman 1989, O'Gorman et al 1987, Eck and
Wells 1987). Several authors theorize that alewife lost their often
observed resiliency when spawner numbers reached their lowest levels in
1983-84 (O'Gorman and Schneider 1986, Wells 1985, Kircheis and Stanley
1981, Stewart and Ibarra 1981). Both predation pressure and competition
with recovering stocks of native fishes have likely played a roll in
suppressing a quick recovery of alewife stocks.

Predation on alewife by salmonines has been estimated to remove 52.9%
of the annual alewife production (Brandt et al. 1991). Although over
half of this predation has been attributed to chinook (Stewart and
Ibarra 1991), heavy predation on adult alewife by lake trout and the
other exotic salmonines, as well as predation in the fall on 20! alewife

by steelhead, coho (Figures 17, 18, and 19), and younger chinook (data

76

not presented here) can be substantial. An increase in the numbers of
stocked lake trout and increased survival of stocked steelhead since the
mid 1980s has likely increased their proportion of the total predation
in Lake Michigan in recent years, particularly with the poorer survival
of chinook observed since 1988. Three native species, yellow perch,
walleye (§§izostedion vitreum), and burbot, are known to consume
alewife, often to the exclusion of other forage during certain times of
the year (Peterson 1993, Wagner 1972). All three have increased in
abundance since the early 19808. There also have been major changes in
the plankton community in Lake Michigan since 1986 and continued
reductions in nutrient inputs (Scavia et al. 1986, Scavia et al. 1988)

that are likely to reduce total community production.

Alggifig and Bloater Abundance

Alewife have been strongly implicated in the past suppression of
several native forage stocks of Great Lakes fish, notably bloater and
yellow perch (Crowder and Binkowski 1983, Miller and Crowder 1990, Brown
et al. 1987, Eck and Wells 1987, Luecke et al. 1989). The increased
abundance of these two species commensurate with the decline in alewife
through the early 19803 might persist if alewife abundance were to
remain at reduced levels. Although bloater and perch can be important
forage species for Lake Michigan salmonines, most perch and large adult
chub typically occupy thermal habitats outside the range preferred by
salmon (warmer water for perch, colder water for bloater). Thus, they
do not present salmon with the abundance of larger prey items that
alewife can. However, prior to the dominance of alewife in Lake

Michigan's forage base, bloaters remained pelagic for longer, and

77

reached larger sizes before moving into their more benthic habitat. As
the alewife population expanded, bloaters began to abandon their pelagic
existence at earlier ages presumably as a compensatory mechanism to
reduce competition (Crowder and Crawford 1984). If reduced interactions
with alewife permits the re-extension of the bloater's pelagic life
history, presence of larger bloaters in the pelagic zone could provide
predators with a large prey item that might functionally replace adult
alewife.

Bloater have traditionally had a higher energy content than alewife,
although in recent years this trend may be reversed (Noguchi 1993) as
bloater continue to show characteristics of density dependent growth
suppression. Bloater are also more efficient in their use of energy
(Stewart and Binkowski 1986), indicating that the system could
theoretically support more bloater production than it has alewife.
Predators might gain more energy from consuming equal rations of bloater
rather than alewife.

There is some concern that higher contaminant levels in bloater
relative to alewife may lead to higher contaminant concentrations in
salmon (Hesselberg 1990, Noguchi et al. 1993, Bowker et al. 1993). If
the more benthic nature of chubs contributes to their higher contaminant
load, then this loading may be more reflective of adult bloaters rather
than the more pelagically distributed juveniles. Consumption of
primarily juvenile bloater by chinook salmon may isolate them somewhat
from this contaminant exposure.

The stability of juvenile bloater as a source of forage may be
questionable. Very low catches (in the USFWS fall forage assessment

surveys) of Y0! bloater since 1991, and of Y0! and yearling bloaters in

78

1992 seem to indicate a trend of poor bloater recruitment in recent
years (Brown et al. 1993). Potential causes under investigation
include: density dependent, compensatory changes in bloater
reproduction; negative interactions (competition and/or predation)
between gyppptpephes and larval bloaters; and renewed competition and
predation by other forage species (Stedman and Argyle 1985, Lehman 1991,
Brown et al. 1993). If successive poor year classes of bloaters are not
offset by increases in alewife or smelt abundance, available forage for
salmon could be reduced, despite the continued abundance of adult

bloater.

n de on of Sam lin Methods

Interpretation of these results is predicated on the acceptance of
some basic assumptions. First, it has been assumed that what is
observed in the stomachs is representative of what was consumed, both in
content and amount. The slight differences in the digested state of
different prey reported here and the likely differences in evacuation
rates of different prey types such as small zooplankton, hard bodied
insects, and large bodied fish, are challenges to this assumption.
Although differences in the digested state between species were small,
smelt and perch may be slightly over-represented in the observed diet
because of their less digested state. The heavier scaling and thicker
skin of these two species may have contributed to this difference
although patterns of diel consumption that differ between prey types
could also explain the observed differences. Larval fish and
zooplankton (other than Bythotrephes) may be under-represented in the

diet because of higher digestion and evacuation rates.

79

The effect of temperature on metabolism and foraging efficiency also
challenge this assumption. However, in this study, the similarity of
water temperature where fish were sampled from (across regions and
seasons) provides no evidence that these effects were substantially
involved in the differing trends observed in diet through seasons and
between basins.

Similarities in the seasonal use of different size prey by the
different salmonine predators likely indicate the opportunistic nature
of these fish. However, the diet of these salmonines may also reflect
the tendency of the sport fishery to select fish inhabiting similar
waters. The sport fishery typically targets certain species at certain
times of the year, taking advantage of when and where the most fish can
be caught. For example, in the early to mid 19803, chinook salmon were
the salmonine species most often sought by anglers throughout most of
the fishing season (Rakoczy and Nelson 1990). Coho salmon were targeted
primarily in the spring along the nearshore waters of southern Lake
Michigan. Steelhead were targeted by many anglers in the fall either
from the further offshore surface waters or from piers. Harvesting of
lake trout was confined to the regulated May 1 - August 15 season, but
targeting was usually limited to periods when chinook were either
difficult to find, or so plentiful that a limit catch of salmon had been
reached.

Because the catch of non-targeted species is common (for example,
catching lake trout while fishing for chinook), the sport fishery does
not always sample each species from its primary habitat or in proportion
to its abundance. This may partially explain the dominance of alewife

in the diets of sport caught lake trout. Angler-caught trout are

80

typically taken from bottom waters within easy boating distance of
shore, a habitat where adult alewife are abundant. Lake trout from
deeper more offshore habitats are known to feed on bloater (Miller and
Holey 1992) but are rarely sought by anglers. Historically, bloaters
were the most common coregonine fed upon by lake trout (Van Oosten and
Deason 1938) and should provide an adequate forage supply for lake trout
and other traditionally deep-water predators. An understanding of the
lakewide distribution of lake trout, and the migration patterns and
habitat preference of the different strains currently being stocked, is
important to interpreting their overall predation on alewife and
bloaters.

The seasonal targeting of species can change from year to year in
response to species abundance. For example, since 1988, the fishery has
changed from one dominated by chinook to a fishery increasingly
dominated by steelhead. Changes in the observed diet over these years
could simply be the result of changed fishing practices, such as the
shift from fishing nearshore waters where chinook used to be plentiful,
to fishing offshore surface waters where steelhead are now plentiful.

The modern Lake Michigan sport fishery evolved during years of an
alewife dominated forage base. Methods of fishing developed during
those years, including depths of water fished and types of lures used,
were likely influenced by the characteristics of alewife. During the
initial years of alewife decline, continued use of these earlier
developed fishing methods may have selected salmonines that were feeding
on alewife over those that had changed their feeding behavior in

response to the changing forage base.

81

Adjusted rations indicated that the smaller size classes of chinook
were apparently consuming more per unit of body weight than the larger
chinook. While this might indicate that forage was more limiting for
the larger fish. It cannot be certain that the lower than expected
apparent ration for large (size-3) chinook was indicative of forage
limitation.

The potential effects that fishing could have on growth have already
been discussed. These same selective tendencies could also influence
how we interpret differences in apparent ration observed between
different size predators. Fishing effort in the mid 19803 culminated 15
years of rapidly increasing catch and effort for chinook salmon in Lake
Michigan (Hansen 1991). In intensively fished salmonid stocks, fishing
has been shown to remove the faster growing (and probably more
aggressively feeding) individuals (Ricker 1981). If this were to occur
in Lake Michigan, then the fish contributing to the sample of larger
fish (mostly age-3 and older), having been exploited for more years, may
not represent the same range of growth and feeding characteristics that
are represented by samples of smaller fish.

The occurrence of empty stomachs is another parameter that can be
influenced by collection methods and procedures. For example, some of
the increased frequency of empty stomachs that was apparent later in the
summer for the sample of the larger chinook was likely related to the
inclusion in the samples of some mature fish that had stopped feeding.
Although collections intentionally did not include mature fish that were
caught in rivers, it likely included some that, although were caught in
Lake Michigan, were in the process of returning to spawn and were no

longer actively feeding. The small difference in the frequency of empty

82

stomachs between male and female size-3 chinook may have been related to
differences in timing of the return of males and females for the
spawning run. These same trends might not have been observed if samples
were collected only from non-maturing fish.

Several studies conducted in Lake Michigan have reported that fish
collected with gill nets have a greater percent of empty stomachs than
fish collected by anglers (Miller and Holey 1992, Hagar 1984). As an
extension of this study, a sample of chinook collected with gill nets
and by anglers from the same waters on the same days were compared.
Although the difference was not statistically significant because of the
small sample size, a slightly higher occurrence of empty stomachs in the
gill netted sample (71% compared to 64% for angler-caught chinook) was
observed.

A lower incidence of empty stomachs in samples of angler-caught fish
versus netted fish has often been attributed to the selection of
actively feeding fish by anglers. While this may be true, digestion and
regurgitation of stomach contents that can occur for fish that are
caught in gill nets or trap nets can also contribute to the same
observed trend. The potential variation in digestion between fish
caught soon after the net is set, and those caught just before it is
pulled, is a complication with diet assessments of netted fish. Because
angler-caught fish are typically put on ice immediately after being
caught, variation in the digestion of prey may be less dependent on when
the fish was caught, and more reflective of actual variation in feeding
times. While regurgitation is often a concern for angler-caught fish,
the same should be true for gill netted fish. Traditionally, gill nets

have been most effectively used at night, while angler-caught fish are

83

most often caught during the day. Diel feeding patterns of salmonines
would, therefore, also contribute to differences in diet for netted and
angled fish. Regardless of the reason, the higher incidence of feeding
fish in angler-caught samples precludes the direct comparison of stomach
fullness or apparent ration between angler caught and netted fish.
However, proportional diet seems to be consistent between netted and
angler-caught fish.

Differences in the decomposition state of prey among different
periods of the day may not be reflective of diel feeding habits if
chinook become satiated on a regular basis and stop feeding. Becoming
regularly satiated, however, would affect the interpretation of several
parameters. Differences in the observed biomass consumed, in numbers of
prey consumed, and in proportion of empty stomachs would be unrelated to
prey abundance, and would be expected to vary without persistent
regional or seasonal trends. If fish regularly became satiated, catch
per effort might vary depending on forage availability, being high when
prey was scarce. This does not seem a likely scenario given its
inconsistency with the data presented and discussed here.

Diet of angler-caught fish admittedly may not be typical of the
entire population of that species. However, it is reasonable to assume
that it is generally representative of those inhabiting the near-shore
environment fished by anglers. Use of the sport fishery as a means of
collecting data for scientific purposes, despite its possible biases,
has many advantages. The lack of a commercial net fishery for these
sport fish has limited sampling alternatives in the Great Lakes to
assessment netting. In comparison, netting can provide only limited

numbers of fish, is comparatively costly and labor intensive, and has

84

substantial bias of its own. Angler-caught fish, in many cases, provide
the only feasible means of collecting adequate numbers of fish from a

geographically wide area.

SUMMARY AND CONCLUSIONS

Sampling angler-caught salmonines provided a cost effective means of
collecting the necessary data capable of adequately describing the diet
of salmonine predators inhabiting the coastal waters of Eastern Lake
Michigan. While alewife, bloater, rainbow smelt, and yellow perch were
the dominant species found in the diet of chinook salmon, the
contribution of each differed across seasons, among predators of
different size, and between predators from the north and south basins.
Predators appeared strongly opportunistic in their foraging.

Differences in the size distribution and in the amount of each prey type
consumed reflected the spatial and temporal distributions of prey and
the thermal habitat overlap between predators and their prey.

Alewife were the dominant prey of larger chinook, particularly in the
northern basin, and bloater were the dominant prey of smaller chinook,
particularly in the southern basin. Smelt were also an important part
of the diet in the northern basin while perch contributed primarily to
the diet of chinook from the southern basin. Chinook salmon consumed
alewife and smelt of all sizes available, but rarely consumed adult
bloater or perch over 160 mm in length, despite their abundance.
Seasonally, both the amount and frequency of prey consumed were highest
in the fall for all sizes of chinook, and in the spring for larger

chinook. These periods coincided with a dominance of young-of-the-year

85

86
fish in the fall diet and a dominance of large adult alewife in the
spring diet.

Chinook from the northern basin typically consumed twice the amount
of alewife and subsequently a greater overall apparent ration than
chinook from the southern basin. Bloater were consumed in nearly equal
amounts by chinook in both basins, but represented a larger percentage
of the diet in the southern basin because of the reduced amount of
overall forage consumed by chinook in the south.

Although alewife may be the species that contributed most to the diet
of an individual chinook that lives to maturity, predation pressure is
heavily influenced by the more abundant younger chinook. For this
reason, bloater account for a substantial and in some locations, the
majority of prey consumed by all chinook inhabiting eastern Lake
Michigan. However, correlations between CPE and amount of prey consumed
indicate chinook may congregate seasonally in different regions of the
lake in response to available prey abundance.

A bloater dominated forage base may not provide as many large prey
individuals for salmon consumption as would an alewife dominated forage
base. But, the present forage assemblage does provide the potential for
sustaining both a reasonable salmon and trout fishery in waters
accessible to anglers (supported by alewife, smelt, and young bloaters)
and a deep water population of lake trout and burbot (supported by adult
bloaters). Such a species mix might have greater potential for
stability than a fishery dependent on one dominant but
characteristically unstable prey species such as alewife.

Unfortunately, with apparent poor recruitment of bloaters in recent

87

years, and the continued inadvertent introductions and subsequent spread
of non-indigenous species, continued instability is likely.

The potential difficulties in accurately measuring growth of chinook,
as well as concern over the potential for and effects of forage
limitation, should lead us to consider additional indices of growth,
condition, and available forage. Measures of stomach fullness or
apparent ration of sport caught fish could be an inexpensive and useful
index of available forage. Direct estimates of total prey consumption
(Noble 1972), using ration data and measurements of evacuation rates,
could also provide an additional method to the bioenergetics approach
for estimating total forage demand by these salmonine predators.
Declines in growth of pelagic piscivores commensurate with the decline
in alewife abundance might be expected, but alone do not dictate
overabundance of predators or poor predator health. Seasonal measures
of lipid content may be good indicators of predator health and
condition.

Despite the frequency of diet studies conducted concurrently for
different regions of Lake Michigan and for different Great Lakes,
differences in collection, in analysis, and in reporting of the data
have prevented complete cross—comparison between studies. Although
characteristics of the basic diet parameters are well documented (Hyslop
1980, Bowen 1983) and quite universally used as norms for reporting diet
data, differences in data stratification and summary often produce large
differences in results. Brief and usually inadequate descriptions of
methods used, although common, often makes it difficult to assess the
comparability of studies and should be a growing concern (Gill 1991).

The lack of coordinated or comparable studies allowing whole lake

88

comparisons have resulted in regional characteristics being
inappropriately, though unavoidably, applied to whole lake systems. If
diet of Great Lakes salmonine predators is to be adequately described,
sample collections need to be comprehensive; including collections
throughout the year, from many different regions, and from all sizes of
each predator species.

With the present increase in coordinated agency assessments and
emphasis on an ecosystem approach to management and research, serious
consideration should be given to the incorporation of coordinated
lakewide diet data into current lakewide assessment and monitoring
programs. The combination of lakewide forage assessment; lakewide
biological assessment of predator fish from sport, net, and escapement
returns; and the lakewide determination of diet of predators could
provide a stronger basis from which to assess the status of the Great

Lakes ecosystem.

APPEND ICES

APPENDIX A

Table 6. Formula used to convert caudal length to total length,
digested state and length to wet weight, and volume to wet
weight for the various prey types.

Ceudal Length (CL) to Total Length (TL):

Alewife: TL = CL * [ 1.172 + ( CL * .000328 ) ]
Bloater: TL = CL * 1.176
Smelt: TL = CL * 1.147
Perch: TL = CL * 1.158

Total Prey Length (TL) to Wet Weight (Wt) given Digested State:

ln WT = ln TL * coeff x - Constant Y

Given: Prey Type
Alewife Bloapgg 5331; Pepph
Diem—e tate .3. .1. .21. _¥_ J. _¥_ .3. .1..
undigested: 3.15 12.6 2.83 11.1 3.18 13.0 3.32 13.0
< 25% digested: 3.30 13.4 2.83 11.1 3.18 13.0 3.16 12.4
> 25% but < 50%: 3.17 12.8 2.54 9.94 2.87 11.7 2.90 11.4
> 50% but < 75%: 2.76 11.3 1.88 7.13 2.23 8.78 2.67 10.3

> 75%, mostly bones: .973 4.55 .973 4.55 .973 4.55 .973 4.55

Volume to Wet Weight:

Wet Weight = Volume * 1.075

89

APEHEHX 8

Location, date, and number (by sex) of each species of salmonine predator sampled in 1986.

Table 7.

Brown Trout

Lake Trout

Steelhead

Coho

Chinook

90

to 0 H010 (Viv-1H H NHN H O

M H Ov-Hn V‘MN O NNO O H

 

he Fir-INF Hr-i IDNQNVO‘IGNO‘WMMH
M N Fl

H m HNH

2' OMMM OO IOMNNNQHQ'NOQNH

n7sfi,~b' '"‘eaéhafaébomwemhwwavmmuI
>~~~~e+g,gn,, as nHH ~-

 

HOOO boon-4v
H

HHHH

I‘HQOH

rtanaax;enmnm.*“

OOIDOVN

some-as
HI-l

OH Q'NHO

H0 10000!

O mum-ha

N v-HOr-GO

NMQO‘
In“ H H

H““ N Wuwfim»fiwgfmfififfiwflffiffifinfifiij

 

Hmvrmninouo ”MI-I
r-h-i MN

hOtNNv-i QON
NHH H H

Ov-HDON V
N H

HFMMI‘
NHH H

HFN‘DOVflN NNH
HH VN

(”MON") H
N H

momma?“ ”WthNm m

rigorfiwunoaeunvuflfiUsnoN
«A , name: ” '7” “'§.H

er Mr: «nu gJ§v,yi

 

 

0 ID‘O‘ONMMQOMM‘O‘OHMVOOHH‘OWDFFMV'VIDHHH‘OQQHN
OOOHHHHNNNNNOOOHHHHHHHHNNNNMCOOOOHH
U\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
avvvvvvvvvvvemnnmmmmnmmmmrnmmmwwomwww
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

flHDmEHDDfllm HD I‘D MEN!“ lfldfllm Q1393!
ZUHBmfihJUh H54 232 “Shun CHDUZ ZQMJU

(cont'd)

Tabbeih

Brown Trout

Trout

Lake

Steelhead

Coho

Chinook

91

[lo HMQVOUM WQQHMQHHOHW
N H H HH

8 HMHWNVN mhmomomosohm
N

n flwmmdow fifiééfififi
‘5 X*.J7 3W~VheMta-H,

 

 

 

 

H H HHH H

H #1 NH HF. H

N yflfigg.gfif§gf, MOI Nwhdm

 

 

MMOHHMH
Nil-1

VQMOOI‘N
NN

‘Iflfihfiégéhfi
“Wyflfififlfifif'

HO OHN

Vine-4MP!

VV HH

GOHVVN

10

11%:

MEN VHF! NH HHWNNI‘G‘DNHVHVOHMNM‘D

SUI-4 000 mm HHOOIDOHQQHMO‘DHFOHVI‘

#94

”‘0 N OQOO
H

VHID‘OI‘MQ‘HID
H N H

WHVIDQUN‘DW
H N N

unfinfiieukuIHrnm{kumuuuhruneuammnecrupmuehaxyouwomomouoouv

N

 

aNMMVQOMMVVMONIDHNNMI‘I‘QQQHNMVVVIDIDID‘DDHNQGQG
pHHHHHNNNNNNNOOHHHHHF‘HHHNNNNNNNNNNNOCOOOO
U\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
aW‘O‘D‘D‘O‘D‘O‘D‘OW‘D‘OI‘FFFI‘FFI‘FFFFI‘l‘l‘l‘l‘l‘f‘l‘hfimmmmmm

OOOOOCOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

4.)
H
0939‘!!!” I10 I") “U 4") 11341113
WQZQmUUJ (DE-'04 HIE" 1:020 Sm moon.

DD
tilt-7|

45” minimum
2140-1 tilt-1290

on:
022

“DQ331116 rs
mzzzzomuzo

(cont'd)

Table 7 .

Steelhead Lake Trout Brown Trout

Coho

Chinook

92

 

 

 

“I HH F1 F1 HH 0
4 vo o 0 NH H
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h‘Nrmn
NVH
2 H
who
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H
4 on o HmH o H Hmvo m ONH MH mm
H
GnHio H. HNH . .,N N «sea v . mfim an bfif
h o o omHH HMHHN NMNNO H monoo va
H H
z N H HMFH OVNNH NVHHH o mNNNH FHN
H H
“A N H HHmN Hhmmm , VFMNM H GNGNH Han
#-
ll‘HHocm: ommmm Hmwvamvvm H H mmeomHHOH
H H N QNNH NN N HH H H NH
onnHm «mowH vwmoommwmn o o vethNNHmm
N ‘NNH (“MI-CH HI-l H H N
“GNmMV «mama memeHbsomm H H mmmHNvawv
H H m menu mmHm_NmHH N N .‘fififi (((((

 

 

G00101010101010FNMVVVOD‘DFQQMVQDFGO‘O‘OOHFI‘mminOv-Hn
uHHHHHHHHHNNNNNMOOOOOHHHHHHHHNNNNNNNOHHN
C\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
amomommmmmoommommmmmmmasmasmasmmasmaimosmmoooo

OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOHHHH

3Dfldfl “flab NHUDRDDDD3QDZM¢MMHDDDD
QQGSQ Haze wHBQmRQQZZmZSUZthQQQQ

:87

 

109 756 400 346 45 42

87

197

236

£11 239

980

1935 959

Totals:

APPENDIX C

The location, date, and number (by size class and sex) of

chinook salmon sampled in 1986.

TflfleB.

size 1 size 2 size 3

Total

 

 

 

 

 

I n

Date

 

 

Port

11 06434075 481 09003 211 20000 30 000 70 002306348
2 2 1
01 12258213 501 81303 131 30000 00 000 61 102215328
21 11 1

12 18682288» 982 90406 342 50000 30 000 32 104511666

fl . ”til .4 41+3fl2:4 . . , .1. 2. 1 . 1

00 13021398 850 70118 691 51501 41 211 51 013817421

1 11 1 1 1

00 02010138 630 35934 782 63511 51 200 91 017831047
1 11 1 1 1

00 15031426  480405042.473 14012 92 411 62 020648468

.. 971 «£2...21:‘11F 111..13 3 1. 1 .11 , .

00 00000230 100 00110 000 30101 01 200 00 100114103

00 03000111 100 01100 100 40112 10 800 01 001014823

00 03000341 200 01210 100 70213 11 000 01 101128926

, 1..

11 19455593 331 79221 802 01602 72 411 21 115227862
11 32 211 1 1 2 1 1 1 11 1 1

01 17268452 231 17337 913 33623 61 000 53 110050188
11 42 311 1 2 1 1 1 21 11 1

1202661394500562096658081503422505033041100950225277940
1 11 32 74 532 1 12 4 3,f 2 1 _ f32 2113

5662339055661340011667734451116881223348033445925122377
0001111222220001111111122223000001111111222222200111111
II/I/ll/l/l/lll///////////////////////Ill/////////////////
44444444444455555555555.3555566666666666.0666666677777777
0000000000000000000000000000000000000000000000000000000

JJH NJ JBABA :BJ UBREUAUB H:WREHAB B:JUHUWUAH ECECR CH AJ HAHWU
SSS GS SGSN SNSL LGFLLMMS 8:PPLGSG NSLGLMLSGS LTLTF FMC MS SSGPL

93

94

(cont'd)

runes.

size 3

size 2
M

size 1

LHJl—JL

Total

_r_1

_M_

JL

F

H-n—

F

JL

 

I

Date

 

 

Port

1392963224 10194150331201 00366 3704125402 1 1 1252011000
2211 1 311 1 1 1
0093370123 51112203241312 25665 8410012431 5 9 2122100000
21 1 1 2 1 11
1385233347 61216353572513 25931 1114137833 6 0 3374111000
44121 _ 1. 2 ,1 . , . 5131 32 ,1 2. .
0072942112 21362271180708 07628 6304050031 0 0 3154010130
11 1 1 1 1 1 1 1 1
1993690024 90304273420209 07784 2423050230 3 1 1110110030
1 1 1 11 1 1
12 11 1,,2,,1 1. 3 3121 12 1 12 2
0150210000 10111020100107 02914 2266063010 0 0 1010000071
1 1
0420210000 10042250020007 01722 4497067031 2 0 1842012133
11
0970420000 20153270220104 03636 6653030041 2 0 2852012104
21 . 1.. 1 1.1 1.... 1 1.
1414015336 41567341511006 09898 1264138443 1 1 5316021101
45131 2 1 1 2 4221 22 2 11 1 1 211 1
1306170147 51458626681518 23061 4220029692 0 0 4074222163
44 11 1 2 2 2 4221 3311 11 1 1 2

21101854730929359672925114107.3869 0548416703501000109381243264
99242 11 1 5 9452 5513 2311 411

88912344455566128999005566667234440667883446799900177885015
1112222222222200000011111.1111222223000001111111122222220112
///////////////////////////////////////////////////////////
77777777777777888888888888888888888999999999999999999990000
00000000000000000000000000000000000000000000000000000001111

 

308179 123 839407 427 808372 430

1955 958 980

Totals:

Table 9.

Values of percent feeding, frequency of occurrence, average

APPENDIX D

number, average weight, percent by number, and percent by
weight for all chinook and for feeding chinook in 1986.

oenc of Dre Occurrence - A11 Itch

Prs z x

mng'mlmmmmmmmm 1.921%!“
W.

 

 

7r een

 

 

 

cl

   

Dre

Occurrence -

 

l’ieh 01th

   

Food

   

 

 

 

 

 

 

 

I -
0113 3 330 0.33 - - - 0.33 - - - - 1.00 - - - 1.00 - - - -
0125-20 0 130 0. 13 - - - - - - - 0. 13 1.00 - - - - - - - 1.00
5110-23 0 500 0.50 - - - - - 0.50 - - 1.00 - - - - - 1.00 - -
5131-0101 0 300 0.30 - - - - 0.25 0.13 - - 1.00 - - - - 0.07 0.33 — -
0100-00 0 750 0.75 - - - - 0 50 0.25 - - 1.00 - - - - 0.07 0 33 - -
0113-10 11 010 0.01 - 0.00 - 0.00 - - - 0.10 1.00 - 0.70 - 0.10 - - - 0.20
0120-7113 21 700 0.70 - 0.00 - - - - - 0.20 1.00 - 0.03 - - - - - 0.30
7120-0102 0 750 0.75 - 0.50 - - - - 0.25 1.00 - 0.07 - - - - - 0.33
0100-10 0 700 0.00 - 0.07 0.22 - - - 1.10 - 0.00 0.20 - - - -
0110-17 30 700 0.77 0.07 0.50 0.07 0.03 - - - 0.10 1.10 0.10 0.71 0.10 0.05 - - - 0.10
0130 15 000 0.03 0.00 0.00 0.07 - - - - 0.07 1.17 0.50 0.50 0.00 - - - - 0.00
0100-07 23 070 1.52 0.17 0.57 0.17 0.20 - 0.00 - 0.30 1.75 0.20 0.05 0.20 0.30 - 0.05 - 0.35
0120-21 20 000 1.00 0._1_5 0.35 0.10 - - 0.12 - 0.3; 1.25 0.10 0.00 0.13 - - 0.13 - 0.30
Am 100 000 0.71 0.05 0.32 1.03 0.05 0.03 0.00 - 0.10
5103-11 3 070 0.07 0.33 - 0.33 - - - - - 1.00 0.50 - 0.50 - - - - -
0112-7/05 3 330 0.33 - - - - - - - 0.33 1.00 - - - - - - - .00
7117-10 50 520 0.01 0.07 0.20 0.02 - 0.02 0.11 - 0.11 1.10 0.10 0.50 0.00 - 0.00 0.21 - 0.21
7122-25 0 300 0.50 0.13 0.30 - - - — - - 1.33 0.33 1.00 - - - - - -
0100-00 0 750 1.25 0.25 0.25 0.50 - - - - 0.25 1.07 0.33 0.33 0.07 - - - - 0.33
0115-10 0 750 1.25 - 0.75 - - - 0.25 - 0.25 1.07 - 1.00 - - - 0.33 - 0.33
0122-20 20 750 1.25 0.20 0.25 0.55 - - 0.10 - 0.15 1.07 0.27 0.33 0.73 — - 0.13 - 0.20
0100 10 700 0.00 0.00 0.20 0.10 - - - - 0.10 1.10 0.57 0.20 0.10 - - - - 0.10
0110-10 7 000 1.20 0.10 0.20 0.71 - - - - 0.10 1.50 0.17 0.33 0.03 - - — - 0.17
0127-20 0 750 1.30 0.25 0.50 0.25 - - 0.13 - 0.25 1.03 0.33 0.07 0.33 - - 0.17 - 0.33
10105-11 13 1000 1.77 0.05 0.31 0.15 - — 0.31 - 0.15 1.77 0.05 0.31 0.15 - - 0.31 - 0.15
10125 0 750 1.00 - 0.75 - r - - I 0.25 - - 1.33 - 1.00 - - — 0.33 - -
Am 130 020 0.07 0.22 0.23 0.10 - 0.00 0.07 - 0.10 1.32 0.20 0.30 0.25 - 0.00 0.00 - 0.33
0112-13 0 00 - - - - - - - - — - - - - - - -
0110-20 0 250 0.75 0.25 0.25 - 0.25 - - - - 3.00 1.00 1.00 - 1.00 - - - -
0125-20 02 200 0.20 0.10 - - - 0.02 - - 0.05 1.00 0.73 - - - 0.00 - - 0.10
5100 20 000 0.50 0.30 0.07 - 0.07 - - - 0.00 1.15 0.77 0.15 - 0.15 - - - 0.00
5110-17 30 300 0.00 0.10 - 0.03 0.03 - 0.00 - 0.12 1.15 0.50 - 0.05 0.05 - 0.15 - 0.00
5123 10 000 0.03 0.21 - - 0.07 - 0.03 - 0.21 1.00 0.25 - — 0.00 - 0.50 - 0.25
5131-0101 03 010 0.00 0.10 - 0.03 0.03 - 0.11 - 0.10 1.12 0.00 - 0.00 0.00 - 0.27 - 0.23
0100-20 11 050 0.73 0.00 0.05 0.00 - - - - 0.00 1.00 0.20 1.00 0.20 - - - - 0.20
7111-13 32 500 0.53 0.00 0.31 - - - - - 0.10 1.00 0.13 0.03 - - - - - 0.31
7120-20 10 030 0.57 0.07 0.07 - 0.21 - — — 0.21 1.33 0.17 0.17 - 0.50 - - - 0.50
0101-02 32 500 0.50 0.00 0.00 - 0.03 - - - 0.03 1.00 0.17 0.70 - 0.00 - — - 0.00
0100—10 27 520 0.50 0.10 0.20 - - - - - 0.15 1.10 0.30 0.50 - - - - - 0.20
0110-17 50 500 0.70 0.12 0.02 0.00 0.00 - - - 0.00 1.20 0.21 0.72 0.10 0.10 - - - 0.10
0130-0107 27 050 1.22 0.07 0.37 0.22 0.01 - - - 0.15 1.03 0.00 0.03 0.20 0.00 - - - 0.17
0110-21 20 770 1.12 0.31 0.30 0.12 0.00 - 0.00 - 0.23 1.05 0.00 0.50 0.15 0.05 - 0.05 - 0.30
Am 012 520 0.00 0.10 0.25 0.00 0.00 0.00 0.03 - 0.11 1.30 0.32 0.50 0.00 0.17 0.00 0.05 - 0.23
5103 20 500 0.07 0.50 - 0.00 - - - - 0.13 1.10 0.00 - 0.07 - - - - 0.21
5111 35 770 0.00 0.77 0.00 - — - - - 0.11 1.22 1.00 0.07 - - - - - 0.15
5120 20 1000 1.05 0.00 0.05 0.10 - - 0.00 - 0.10 1.05 0.00 0.05 0.10 - - 0.00 - 0.10
0112-13 20 050 0.55 0.00 - - 0.05 - - - 0.10 1.22 0.00 - - 0.11 - - - 0.22
0125 17 050 0.71 0.05 - 0.00 - - - - - 1.00 1.00 - 0.00 - - - - -
7102-00 12 500 0.07 0.25 0.17 - - - - - 0.25 1.33 0.50 0.33 - - - - - 0.50
7117-10 00 030 0.50 0.20 0.00 0.10 - 0.03 0.02 - 0.07 1.35 0.05 0.10 0.23 - 0.00 0.00 - 0.15
7121-23 33 210 0.21 0.00 0.00 - - - - - 0.00 1.00 0.03 0.20 - - - - - 0.20
7120-25 15 330 0.33 0.07 - 0.07 - — - - 0 20 1.00 0.20 - 0.20 - - - - 0.00
0100-00 0 500 0.03 0.13 0.13 0.30 - - - - - 1.25 0.25 0.25 0.75 - - - - -
0115-10 03 530 0.05 0.20 0.10 - - 0.02 0.07 - 0.12 1.22 0.00 0.35 - - 0.00 0.13 - 0.22
0122-20 70 020 0.70 0.01 0.00 0.10 - 0.01 0.00 - 0.07 1.23 0.00 0.13 0.20 - 0 02 0 00 - 0.11
0100 22 020 1.27 0.00 0.10 0.32 - - - - 0.00 1.50 0.03 0.22 0.30 - - - - 0.11
0110-10 10 000 1.00 0.50 0.20 0.00 - - - - 0.10 1.70 0.50 0.22 0.00 - - - - 0.11
0127-20 10 1000 1.30 0.57 0.20 0.10 - - 0.10 - 0.21 1.30 0.57 0.20 0.10 - - 0.10 - 0.21
10110-11 7 1000 1.71 0.00 0.20 0.10 - -_ 0.10 - 0.20 1.71 0.00 0.20 0.1__0 - - 0.10 - 0.2;
Am 010 000 0.03 0.00 0.11 0.15 0.01 0.00 0.11 - 0.12 1.32 0.00 0.15 0.20 0.01 0.01 0.12 - 0.10
W
0105-00 3 00 - - - - - - - - - - - - - - - - - -
0112-13 15 70 0.13 - - - - 0.07 - - 0.07 2.00 - - — - 1.00 — - 1.00
0110-20 20 500 0.50 0.00 0.05 - 0.05 - - - - 1.00 0.00 0.10 - 0.10 - - - -
0125-20 10 500 0.50 0.50 - - - - - - - 1.00 1.00 - - - - - - -
5100 10 000 0.01 0.30 0.00 - 0.00 - - 0.00 0.00 1.30 0.00 0.13 - 0.13 - - 0.13 0.13
5110-17 10 500 0.00 0.00 - - - - - - 0 20 1.20 0.00 - - - - - - 0.00
5123 3 070 0.07 0.07 - - — - - - - 1.00 1.00 - - — - - - -
5131 5 000 0.00 0.00 - 0.20 - - - - - 1.33 1.00 - 0.33 - - - - -
0120-7113 20 000 0.00 0.25 0.00 - - - - - 0.13 1.00 0.55 0.10 - - - - - 0.27
7120-20 13 000 0.02 0.00 0.15 - 0.15 - - - 0.23 1.33 0.17 0.33 - 0.33 - — - 0.50
0101-02 27 330 0.00 0.11 0.11 0.07 0.11 - - - 0.00 1.33 0.33 0.33 0.22 0 33 - - - 0.11
0100-10 20 500 0.50 0.21 - - - - - - 0.33 1.00 0.02 - - - - - - 0.07
0110-17 22 550 0.73 0.10 0.01 0.05 0.05 - - - 0.05 1.33 0.33 0.75 0.00 0.00 - - - 0.00
0130-0107 0 750 1.13 0.25 0.13 0.13 0.50 - - - 0.13 1.50 0.33 0.17 0.17 0.07 - - - 0.17
0110-21 20 100 0.23 0.00 - 0.12 0.00 - - - 0.00 1.20 0.20 - 0.00 0.20 - - - 0.2_0_
[W 230 000 1.25 0.50 0.15 0.11 0.15 0.00 - 0.01 0. 3
5103 00 730 0.00 0.05 - 0.02 0.02 - - 0.02 0.12 1.10 0.00 - 0.03 0.03 - — 0.03 0.17
5110-11 00 070 0.77 0.50 0.02 0.07 - - - - 0.10 1.15 0.00 0.03 0.10 - - - - 0.15
5120 0 500 0.50 0.17 - - - - 0.33 - - 1.00 0.33 - - - - 0.07 - -
0112-13 7 710 0.00 0.71 - 0.10 - — - - - 1.20 1.00 - 0.20 - - - - -
0125 15 730 0.00 0.07 0.07 - - - — - 0.07 1.00 0.01 0.00 - - - - - 0.00
7105 20 500 0.50 0.33 0.00 0.00 - - - 0.00 1.00 0.07 0.17 0.00 - - - - 0.17
7117-10 100 310 0.30 0.17 0.00 0.00 - - 0.02 - 0.07 1.10 0.50 0.22 0.00 - - 0.00 - 0.23
7121-23 50 320 0.00 0.20 0.00 0.00 - - - 0.02 0.00 1.25 0.03 0.10 0.10 - - - 0.00 0.10
7120-25 23 570 0.70 0.35 0.17 0.13 - - - - 0.00 1.31 0.02 0.31 0.23 - - - - 0.15
0100-10 10 700 1.00 0.20 0.20 0.00 - - - - - 1.03 0.20 0.20 0.00 - - - - -
0115-10 03 030 0.01 0.00 0.13 0.02 - — 0.03 - 0.10 1.20 0.75 0.20 0.03 - - 0.05 - 0.25
0122-20 00 070 0.00 0.00 0.05 0.20 - - - 0.01 0.00 1.25 0.71 0.00 0.30 - - - 0.02 0.00
0100-00 10 500 0.00 0.30 0.10 0.10 - - - - 0.13 1.50 0.07 0.33 0.33 - - - - 0.22
0110-10 22 500 0.01 0.32 0.10 0.01 - - - - 0.05 1.50 0.50 0.23 0.00 - - - - 0.00
0127-10105 10 500 0.03 0.20 0.10 0.20 - - - - 0.21 1.00 0.57 0.2; 0.57 - - - - 0.03
I“ 501 500 0.70 0.00 0.00 0.10 0.00 - 0.00 0.00 0.00 1.31 0.00 0.15 0.27 0.00 - 0.00 0.00 0.10

96

Table 9 . (cont 'd)

“er of Ir - A11 Chinook 00.0.;- o! D - Chinook 01th Food
anmmlmummmmmmmnllmuummmmmml
w

 

 

 

 

 

 

 

 

 

 

 

 

0113 3 330 0.33 - - - 0.33 - - 1.00 - - - 1.00 -
0125-20 0 130 0.25 - - - - - - - 0.25 2.00 - - - - - - 2.00
5110-23 0 500 - - - - - - 100.3 - - - - - - - - 210.5 - -
5131-0101 0 300 - - - - - - 0.13 - - - - - - - - 0.33 -
0100-00 0 750 - - - - - 17.50 0.25 - - - - - - - 23 33 0.33 - -
0113-10 11 010 1.30 - 1.00 - 0.00 - - - 0.10 1.50 - 1.20 - 0.10 - - - 0.20
0120-7113 21 700 1.33 - 1.05 - - - - - 0.20 1.75 - 1.30 - - - - - 0.30
7120-0102 0 750 1.00 - 0.75 - - - - - 0.25 1.33 - 1.00 - - - - - 0.33
0100-10 0 700 1.00 - 1.11 0.33 - - - - - 1.00 - 1.03 0.03 - - - - -
0110-17 30 700 1.57 0.13 0.00 0.07 0.07 - - - 0.10 2.20 0.10 1.10 0.07 0.10 - - - 0.10
.I’. 15 000 50” .07, .0‘1 .0.’ ‘ ' - ‘ .001 ‘0‘, '0’: .0” .0” ' " ' .0“
0100-07 23 070 0.30 0.17 1.52 0.00 1.70 - 0.70 - 0.30 0.05 0.20 1.75 0.55 2 00 - 10.05 - 0.05
0120-21 20 000 2.10 0.25 1.35 0.15 - - 12.15 - 0.35 2.03 0.31 1.00 0.10 - - 15.10 - 0.00
Am 100 000 1.10 0.00 0.03 0.00 0.10 0.73 10.00 - 0.17 1.50 .1 .70 0. .20 0.07 20.02 - 0.
5103-11 3 070 1.33 1.00 - 0.33 - - - - - 2.00 1.50 - 0.50 - - - - -
0112-7105 3 330 0.33 - - - - - - - 0.33 1.00 - - - - - - - 1.00
7117-10 50 520 0.50 0.07 0.35 0.02 - 0.00 20.00 - 0.15 1.10 0.10 0.00 0.00 - 0.11 50.07 - 0.20
7122-25 0 300 0.75 0.25 0.50 - - - - - - 2.00 0.07 1.33 - - - - - -
0100-00 0 750 1.25 0.25 0.25 0.50 - - - - 0.25 1.07 0.33 0.33 0.07 - - - - 0.33
0115-10 0 750 2.00 - 1.75 - - - 12.00 - 0.25 2.07 - 2.33 - - - 10.00 - 0.33
0122-20 20 750 0.05 0.50 0.25 3.15 - - 30.05 - 0.15 5.00 0.07 0.33 0.20 - - 52.07 - 0.20
0100 10 700 1.50 1.10 0.20 0.10 - - - - 0.10 2.10 1.57 0.20 0.10 - - - - 0.10
0110-10 7 000 0.57 0.10 0.57 5.71 - - - - 0.10 7.07 0.17 0.07 0.07 - - - - 0.17
0127-20 0 750 3.00 1.00 1.50 0.25 - - 13.00 - 0.25 0.00 1.33 2.00 0.33 - - 10.50 - 0.33
10105-11 13 1000 0.31 7.00 0.50 0.15 - - 10.50 - 0.15 0.31 7.00 0.50 0.15 - - 10.50 - 0.15
10125 0 750 2.00 - 2.00 - - - 1.25 - - 2.07 - 2.07 - - - 1.07 - -
00000.0 150 iii fiat 1.07 0.0—0' 0.03 - 0.00 0.00 - 0.10 0.01 i. . . 0 - 0.00 0.00 - 0.30
0112-13 0 00 - - - - - - - - - - - - - - - - - -
“5"” ‘ 250 10’, .01, .0” " .0“ ' ' ‘ ' ,0” 10.. 10.. ' 10.. ‘ ‘ - "
0125-20 02 200 0.00 0.30 - - - 0.10 - - 0.05 1.55 1.30 - - - 0.73 - - 0.10
”0‘ I. 000 00“ .0“ '0', ‘ .001 ' ' ' .0.‘ 10,. 50.. .055 ’ .015 ' - ' .00.
5110-17 30 300 0.00 0.05 - 0.03 0.03 - 00.07 - 0.15 1.00 1.35 - 0.05 0.05 - 112.0 - 0.05
5123 10 000 0.50 0.21 - - 0.07 - 200.0 - 0.21 0.50 0.25 - - 0.00 - 200.7 - 0.25
5131-0101 03 010 0.01 0.25 - 0.03 0.03 - 11.13 - 0.10 1.00 0.02 - 0.00 0.00 - 20.00 - 0.23
0100-20 11 050 1.27 0.00 1.00 0.00 - - - - 0.00 2.00 0.20 2.20 0.20 - - - - 0.20
7111-13 32 500 0.72 0.13 0.00 - - - - - 0.10 1.00 0.25 0.00 - - - - - 0.31
7120-20 10 030 1.10 0.10 0.21 - 0.03 - - - 0.30 2.07 0.33 0.50 - 1.00 - - - 0.03
0101-02 32 500 1.00 0.00 0.00 - 0.00 - - - 0.03 1.00 0.17 1.50 - 0.11 - - - 0.00
0100-10 27 520 1.15 0.20 0.70 - - - - - 0.15 2.21 0.50 1.03 - - - - - 0.20
0110-17 50 500 1.30 0.22 0.72 0.20 0.00 - - - 0.00 2.30 0.30 1.20 0.00 0.10 - - - 0.10
.I’."/.1 2, .5. ‘0‘! .05’ .07. 301. 301’ ' ’ ' .0“ 10” .051 .0’5 ’0“ 10“ ' ' ' .05,
0110-21 20 770 2.35 0.01 0.73 0.31 0.00 - 0.00 - 0.00 3.05 1.05 0.05 0.00 0.05 - 1.15 - 0.00
0.0n.- 0W" .0 .a .5 . 0 0.30 0.01 n.n - 070' .00 0. a 1.00 . 0.50 0.0: $021: — 0.55'
5103 20 500 1.50 1.21 - 0.00 - - - - 0.25 2.00 2.07 - 0.10 - - - - 0.03
5111 35 770 3.07 3.00 0.00 - - - - - 0.11 5.15 0.03 0.07 - - - - - 0.15
5120 20 1000 1.05 1.20 0.05 0.10 - - 303.0 - 0.10 1.05 1.20 0.05 0.10 - - 303.0 - 0.10
0112-13 20 050 1.05 0.05 - - 0.10 - - - 0.10 2.33 1.00 - - 0.22 - - - 0.22
0125 17 050 2.00 2.02 - 0.00 - - - - - 0.05 0.30 - 0.00 - - - - -
7102-00 12 500 3.00 2.00 0.07 - - - - - 0.25 0.00 0.17 1.33 - - - - - 0.50
7117-10 00 030 0.00 0.35 0.13 0.12 - 0.07 0.13 - 0.00 1.50 0.01 0.31 0.27 - 1.50 0.31 - 0.10
7121-23 33 210 0.27 0.00 0.12 - - - - - 0.00 1.20 0.03 0.57 - - - - - 0.20
7120-25 15 330 0.33 0.07 - 0.07 - - - - 0.20 1.00 0.20 - 0.20 - - - - 0.00
0100-00 0 500 1.13 0.25 0.25 0.03 - - - - - 2.25 0.50 0.50 1.25 - - - - -
0115-10 03 530 1.12 0.37 0.03 - - 0.02 0.00 - 0.12 2.00 0.70 1.17 - - 0.00 12.70 - 0.22
0122-20 70 020 1.20 0.00 0.00 0.30 - 0.05 5.53 - 0.07 1.00 1.00 0.15 0.02 - 0.00 0.00 - 0.11
0100 22 020 3.05 1.77 0.10 0.00 - - - - 0.23 3.72 2.17 0.22 1.00 - - - - 0.20
0110-10 10 000 10.00 1.00 0.30 0.50 - - - - 0.10 12.11 1.11 0.33 10.50 - - - - 0.11
0127-20 10 1000 5.30 0.30 0.50 0.10 - - 0.00 - 0.30 5.30 0.30 0.50 0.10 - - 0.00 - 0.30
10110-11 7 1000 7.03 0.20 2.57 0.10 - - 20.20 - 0.03 7.03 0. 20 2.57 0.10 -_ - 20.20 - 0.03
0.0:..- W """_T?Z:.n . 0.00 031 0.0i 0.0) 3).-'05 - 0.15 —.—i3 10 Iii 0.03 0.01 0. a 0.01 30.32 - 0.2T
0105-00 3 00 - - - - - - - - - - - - - - - - -
0112-13 15 70 0.07 - - - - 0.27 - - 0.07 1.00 - - - - 0.00 - - 1.00
0110-20 20 500 1.00 1.30 0.05 - 0.05 - - - - 2.00 2.00 0.10 - 0.10 - - - -
0125-20 10 500 1.50 1.50 - - - - - - - 2.00 2.00 - - - - - - -
5100 10 000 1.20 1.00 0.00 - 0.00 - - 0.00 0.00 2.00 2.30 0.13 - 0.13 - - 0.13 0.13
”1"11 5. ”0 50” 501. ' ‘ ' ‘ ' " .02. 10“ 10’. ' ’ ' " ‘ ' .0“
5123 3 070 0.07 0.07 - - - - - - - 1.00 1.00 - - - - - - -
5131 5 000 1.00 1.20 - 0.20 - - - - - 2.33 2.00 - 0.33 - - - - -
0120-7113 1‘ 000 .0” .0” .0” ' ‘ ' ‘ ‘ .05) 50” .0“ .01. ' ' ‘ ’ ’ '0’,
7120-20 13 000 0.02 0.00 0.23 - 0.31 - - - 0.31 2.00 0.17 0.50 - 0.07 - - - 0.07
0101-02 27 330 0.03 0.11 0.10 0.07 0.22 - - - 0.00 1.00 0.33 0.50 0.22 0.07 - - - 0.11
0100-10 20 500 0.03 0.00 - - - - - - 0.30 1.07 0.02 - - - - - - 0.75
'I!"21 2’ 550 50“ .05. .0’5 .0.’ .01. ' ‘ ‘ .0.’ an“ '0’, 50‘? .0” .033 ' ' ‘ .0“
0130-0107 0 750 2.13 0.25 0.13 0.30 1.25 - - - 0.13 2.03 0.33 0.17 0.50 1.07 - - - 0.17
0110-21 20 100 0.27 0.00 - 0.15 0.00 - - - 0.00 1.00 0.20 - 0.00 0.20 - - - 0.20
.w 230 3‘ .05. 0 50 01’ 0 .032 .011 ' .001 .0
5103 00 730 3.00 2.01 - 0.02 0.02 - - 0.02 0.01 0.10 3.50 - 0.03 0.03 - - 0.03 0 50
5110-11 00 070 0.23 0.03 0.02 0.00 - - - - 0.10 0.35 0.05 0.03 0.13 - - - - 0.15
5120 0 500 0.17 0.17 - - - - 0.03 - - 0.33 0.33 - - - - 0.07 - -
0112-13 7 710 2.20 2.10 - 0.10 - - - - - 3.20 3.00 - 0.20 - - - - -
0125 15 730 2.33 2.20 0.07 - - - - - 0.07 3.10 3.00 0.00 - - - - - 0.00
7105 20 500 2.75 2.21 0.33 0.00 - - - - 0.13 5.50 0.02 0.07 0.17 - - - - 0.25
7117-10 100 310 0.50 0.20 0.10 0.00 - - 0.00 - 0.07 1.50 0.70 0 00 0.10 - - 0.25 - 0.23
7121-23 50 320 0.00 0.20 0.00 0.00 - - - 0.02 0.00 1.30 0.03 0.25 0.25 - - - 0.00 0.10
7120-25 23 570 1.00 0.70 0.30 0.22 - - - - 0.00 2.02 1.30 0.00 0.30 - - - - 0.15
.I“-5. 5. 7.. ’0” .0” .0“ 20.. ’ ’ ' ‘ ' ‘07! '0‘, .02. ‘0” ' ' ' ' '
0115-10 03 030 1.00 0.05 0.10 0.02 - - 2.17 - 0.20 2.20 1.50 0 30 0.03 - - 3.03 - 0.30
0122-20 00 070 2.02 1.00 0.10 1.05 - - - 0.01 0.05 3.00 2.10 0.10 1.57 - - - 0.02 0.00
0100-00 10 :0 2.00 1.10 0.10 0.50 - - - - 0.13 3.50 2.11 0.33 0.00 - - - - 0.22
0110-10 0.10 0.50 0.10 1.50 - - - ' - 0.05 10.00 7.02 0.23 2.50 - - - - 0.00
0127-10105 :0 500 3.03 2.10 0.21 0.70 - - - - 0.20 0. 00 0. 20 0.03 1.57 - - - - 0.57
I” 501 2.00 1.00 0.13 0.51 0.00 - 0.02 0.00 0.10 0.00 2.70 0.20 0.00 0.00 - 1.21 0.00 0.10

Table 9.

MJW
W

0113 3 330
0125-20 0 130
5110-23 0 500
5131-0101 I 300
0100-00 0 150
0113-10 11 510
0120-7113 21 100
1120-0102 0 150
0100-10 0 700
0110-11 30 700
0130 15 000
0150-01 23 010
0120-21 20 000
Average 100 000
5103-11 3 070
0112-1105 3 330
1111-10 50 520
1122-25 0 300
0100-00 0 150
0115-10 0 150
0122-20 20 150
0100 10 100
0110-10 7 000
0121-20 0 150
10105-11 13 1000
10125 0 150
2000090 130 020
0112-13 0 00
0110-20 0 250
0125-20 02 200
5100 20 000
5110-17 30 300
5123 10 000
5131-0101 03 010
0100-20 11 050
1111-13 32 500
1120-20 10 030
01.1-02 32 500
0100-10 27 520
0110-11 50 500
0130-9101 21 050
0110-21 20 110
Average 012 520
W

5103 20 500
5111 35 110
5120 20 1000
0112-13 0 050
0125 17 050
1102—00 12 500
1111-10 00 030
1121-23 33 210
1120-25 15 330
0100-00 0 500
0115-10 03 530
0122-20 70 020
0100 22 020
0110-10 10 000
0121-20 10 1000
10110-11 1 1000
Avereqe 010 000
0105-00 3 00
0112-13 15 70
0110-20 20 500
0125-20 10 500
5100 10 000
5110-17 10 500
5123 3 010
5131 5 000
0120-1113 20 000
1120-20 13 000
0101-02 21 330
0100-10 20 500
0110-17 22 550
0130-0/07 0 150
0110-21 20 100
Avereoe 230 000
5101 00 131
5110-11 00 070
5120 0 500
0112-13 1 110
0125 15 130
1105 20 500
1117-10 100 310
1121-23 50 320
1120-25 23 510
0100-10 10 100
0115—10 03 030
0122-20 00 010
0100-00 10 500
0110-10 22 550
0121-10105 10 500
Iverege 501 500

(cont'd)

 

l0roent o! Dre lueber - All Chinook

97

 
 

 

 

 

 

100.0 - - - 100.0 - -
100.0 - - - - - 100.0
100.0 - 00.0 - 0.7 - 13.3
100.0 - 70.0 - - - 21.0
100.0 - 75.0 - - - 25.0
100.0 - 70.0 23.1 - - -
100.0 0.5 51.1 20.0 0.3 - 0.0
100.0 55.0 35.0 5.0 - - 5.0
100.0 0.0 35.0 11.1 00.0 - 0.1
_109.0 11.0 91-3 1.1 - - 16.7
100.0 7.3 50.0 7.0 12.0 - 15.0
100.0 75.0 - 25.0 - - '
100.0 - - - - - 100.0
100.0 12.5 50.0 3.1 - - 25.0
100.0 33.3 00.7 - - - -
100.0 20.0 20.0 00.0 - - 20.0
100.0 - 07.5 - - — 12.5
100.0 12.3 0.2 77.0 - - 3.7
100.0 73.3 13.3 0.7 - - 0.7
100.0 2.2 0.7 07.0 - - 2.2
100.0 33.3 50.0 0.3 - - 0.3
100.0 00.0 0.5 1.0 - - 1.0
100.0 - 100.0 - - - -
100.0 .3 10.7 27.1 - - 0.0
100.0 20.0 00.0 - 00.0 - -
100.0 00.2 - - - - 11.0
100.0 72.2 11.1 - 11.1 - 5.0
100.0 07.0 - 0.7 0.7 - 22.0
100.0 02.0 - - 10.3 - 02.0
100.0 01.5 - 7.7 7.7 - 23.1
100.0 7.1 70.0 7.1 - - 7.1
100.0 17.0 00.0 - - - 21.7
100.0 12.5 10.0 - 37.5 - 31.3
100.0 0.0 02.0 - 5.0 - 2.0
5000' 220‘ 00.5 ' ' " 510’
100.0 15.0 52.2 20.3 5.0 - 5.0
100.0 2.3 12.1 03.0 30.7 - 7.5
100.0 30.0 3_1.1 13.1 1.0 - 10.7
100.0 10.1 30.3 20.1 20.7 - 10.0
100.0 70.0 - 5.0 - - 10.2
100.0 05.7 1.0 - - - 2.0
100.0 02.0 3.0 0.0 - - 0.0
100.0 01.0 - - 0.5 - 0.5
100.0 00.0 - 2.0 - -
100.0 00.0 22.2 - - - 0.3
100.0 51.2 10.5 17.1 - - 12.2
100.0 33.3 00.0 - - - 22.2
100.0 20.0 - 20.0 - - 00.0
5.00. 5101 120’ 550‘ ' " '
100.0 33.3 50.3 - - - 10.0
100.0 50.0 7.7 31.0 - - 5.5
100.0 50.2 0.0 20.0 - - 7.5
100.0 0.2 2.0 07.2 - - 0.0
100.0 01.3 0.3 2.7 - - 0.7
100.0 57.7 30.0 $3.0 - - 5.0
100.0 57.1 11.2 20.0 0.0 - 5.3
100.0 - - - - - 100.0
100.0 02.0 3.0 - 3.0 - -
100.0 100.0 - - - - -
100.0 02.0 0.3 - 0.3 0.3 0.3
100.0 00.0 - - - - 15.0
100.0 100.0 - - - - -
100.0 05.7 - 10.3 - - -
100.0 50.3 10.7 - - - 25.0
100.0 0.3 25.0 - 33.3 - 33.3
100.0 17.0 20.0 11.0 35.3 - 5.0
100.0 55.0 - - - - 05.0
100.0 13.3 00.7 3.3 13.3 - 3.3
100.0 11.0 5.0 17.0 50.0 - 5.0
100.0 10.3 - 57.1 10.3 - 10.3
100.0 51.0 11.2 7.0 10.0 0.3 0.7
100.0 00.0 - 0.7 0.7 0 7 13.2
100.0 05.3 0.0 2.0 - - 2.0
100.0 100.0 - - - - -
100.0 03.0 - 0.3 - - -
50.0. ,‘0J 20’ ’ ' ' 20’
100.0 00.3 12.1 3.0 - - 0.5
100.0 00.0 27.1 11.3 - - 10.7
100.0 05.5 10.2 10.2 - 0.5 13.0
100.0 52.0 20.5 10.7 - - 5.0
100.0 0.1 0.1 00.0 - - -
100.0 00.2 13.0 1.1 - - 17.0
100.0 53.7 3.7 00.2 - 0.0 2.0
100.0 50.0 0.0 25.0 - - 0.3
100.0 72.0 2.2 20.3 - - 0.7
100.0 02.5 0.3 22.0 - - 0.3
100.0 00.0 5.2 21.1 0.0 0.1 0.2

 

 

Percent of 3 Ineber - Chinook lith !ood
IEHMMMIHMMMI

 

 

 

 

 

 

100.0 - - - 100.0 - -
100.0 - - - - - 100.0
100.0 - - - - - -
100.0 - - - - - -
100.0 - - - - - -
100.0 - 00.0 - 0.7 - 13.3
100.0 - 70.0 - - - 21.0
100.0 - 75.0 - - - 25.0
50.0. - ,‘0, 2305 - ‘ ‘
100.0 0.5 51.1 20.0 0.3 - 0.0
5.00. ’50. 350. 50. ’ ' 50.
100.0 0.0 35.0 11.1 00.0 - 0.1
_129.0 11.0 00.3 7.1 - - 10.7
100.0 0.0 00.7 7.0 12.7 - 20.2
100.0 75.0 - 25.0 - - -
100.0 - - - - - 100.0
100.0 12.5 50.0 3.1 - - 25.0
100.0 33.3 00.7 - - - -
100.0 20.0 20.0 00.0 - - 20.0
100.0 - 07.5 - - - 12.5
100.0 12.3 0.2 77.0 - - 3.7
100.0 73.3 13.3 0.7 - - 0.7
100.0 2.2 0.7 07.0 - - 2.2
100.0 33.3 50.0 0.3 - - 0.3
100.0 00.0 0.5 1.0 - - 1.0
39.0 - 100.0 ; - - -
00.0 0 .3 21.7 25.0 - - 11.1
100.0 20.0 00.0 - 00.0 - -
100.0 00.2 - - - - 11.0
100.0 72.2 11.1 - 11.1 - 5.0
100.0 71.1 - 2.0 2.0 - 23.7
100.0 02.0 - - 10.3 - 02.0
100.0 01.5 - 7.7 7.7 - 23.1
100.0 7.1 70.0 7.1 - - 7.1
100.0 17.0 00.0 - - - 21.7
100.0 12.5 10.0 - 37.5 - 31.3
5°00. .0. .10‘ ' 30’ ' 20’
5000. 320‘ 00.5 ' " ‘ 520’
100.0 15.0 52.2 20.3 5.0 - 5.0
100.0 2.3 12.1 03.0 30.7 - 7.5
100.0 30.0 31.1 13.1 1.0 - 10.7
100.0 10.0 30.5 10.1 10.3 - 11.1
100.0 70.0 - 5.0 - - 10.2
50.0. ’50, 50‘ ’ " ' 10’
50.0. .20. 30‘ ‘0’ ‘ ‘ ‘0,
100.0 01.0 - — 0.5 - 0.5
100.0 00.0 - 2.0 - - -
100.0 00.0 22.2 - - - 0.3
100.0 51.2 10.5 17.1 - - 12.2
100.0 33.3 00.0 - - - 22.2
100.0 20.0 - 20.0 - - 00.0
100.0 22.2 22.2 55.0 - - -
5.00. 310’ “0) - ' " 5.0‘
5.00. “0’ 101 ’50, " ' 505
100.0 50.2 0.0 20.0 - - 7.5
100.0 0.2 2.0 07.2 - - 0.0
100.0 01.3 0.3 2.7 - - 0.7
49.0 51.1 34.0 1.0 - - 5.0
100.0 57.0 11.3 20.0 0.0 - 0.2
100.0 - - - - - 100.0
100.0 02.0 3.0 - 3.0 - -
100.0 100.0 - - - - -
100.0 02.0 0.3 - 0.3 0.3 0.3
100.0 00.0 - - - - 15.0
100.0 100.0 - - - - -
100.0 05.7 - 10.3 - - -
100.0 50.3 10.7 - - - 25.0
100.0 0.3 25.0 - 33.3 - 33.3
5.00. 510‘ ”0‘ 550. 3503 ' 50’
5.°0. 550. ' - ' ' ‘50.
100.0 13.3 00.7 3.3 13.3 - 3.3
100.0 11.0 5.0 17.0 50.0 - 5.0
_1_03.0 11.3 - 57.1 14.3 - 14.3
100.0 51.5 11.5 0.1 10.2 0.0 12.0
100.0 00.0 - 0.7 0.7 0.7 13.2
100.0 05.3 0.0 2.0 - - 2.
100.0 100.0 - - - - -
100.0 03.0 - 0.3 - - -
100.0 00.3 2.0 - - - 2.0
100.0 00.3 12.1 3.0 - - 0.5
100.0 00.0 30.0 0.0 - - 10.2
100.0 05.5 10.2 10.2 - 0.5 13.0
100.0 52.0 20.5 10.7 - - 5.0
100.0 0.1 0.1 00.0 - - -
100.0 00.2 13.0 1.1 - - 17.0
100.0 53.7 3.7 00.2 - 0.0 2.0
100.0 50.0 0.0 25.0 - - 0.3
100.0 72.0 2.2 20.3 - - 0.7
100.0 02.5 0.3 22.0 - - 0.3
100.0 00.7 5.0 20.0 0.0 0.1 0.5

Table 9.

(cont'd)

98

I01 it o! 0 - A11 7100
W

 

 

 

 

 

 

“I, 3 3’. .01. ' ' ‘ .01. ’ " ‘ ‘
0125-20 0 130 0.13 - - - - - - - 0.13
5110-23 0 500 2.71 - - - - - 2.71 — -
5131-0101 0 300 0.01 - - - - 0.01 0.00 - -
0100-00 0 750 2.30 - - - - 2.30 0.00 - -
0113-10 11 010 0.35 - 3.01 - 0.00 - - - 0.30
0120-7113 21 700 0.50 - 0.13 ~ - - - - 0.37
7’“‘.’.’ . 1,. .0.‘ ’ ’0.‘ ' ' ' ' ' .0"
0100-10 0 700 0.03 - 0.00 0.70 - - - - -
0110-17 30 700 0.20 0.00 0.00 0.13 0.07 - - - 0.02
0130 15 000 0.07 1.10 3.50 0.20 - - - - 0.01
0100-07 23 070 11.00 2.00 5.00 1.00 1.03 - 0.00 - 0.03
0120-21 20 000 0.07 0.50 2.70 0.00 - - 0.0_0 - 0.0_0_
00.0090 100 000 3.00 0. 2.07 .10 0.20 0.10 0.35 - 0.10
5103-11 3 070 0.03 0.17 - 0.27 - - - - -
0112-7105 3 330 0.70 - - - - - - - 0.70
7117-10 50 520 1.55 0.10 1.17 0.00 - 0.00 0.03 - 0.10
1’12’23 . 300 ’0“ .0“ 50” ' ' ‘ " " ’
0100-00 0 750 0.00 0.15 3.20 1.05 - - - - 0.33
.’5,‘1‘ ‘ 750 10“ ' ‘0’, " ’ .013 ' .0“
0122-20 20 750 10.00 3.01 2.01 0.00 - - 0.00 - 0.23
0100 10 700 23.50 20.00 2.77 0.77 - - - - 0.02
0110-10 7 000 23.00 0.07 1.51 21.00 - - - - 0.17
0127-20 0 750 0.07 1.00 7.00 0.23 - 0.07 - 0.20
10105-11 13 1000 11.05 0.00 1.50 0.02 - - 0.15 - 0.02
10125 0 750 0.03 - 0.03 - - - 0.01 - -
00.300 130 020
0112-13 0 00 - - - - - - - - -
0110-20 0 250 7.75 0.55 0.03 - 2.50 - - - -
0125-20 02 200 2.00 2.57 - - - 0.03 - - 0.00
5100 20 000 0.37 7.00 0.10 - 0.10 - - - 0.01
5110-17 30 300 2.03 1.57 - 0.37 0.20 - 0.37 - 0.13
5”: 0‘ “. 10.1 .01, - ’ .0.‘ ' 307‘ ’ .035
5131-0101 03 010 3.05 2.00 - 0.05 0.32 - 0.07 - 0.00
0100-20 11 050 0.00 0.00 0.27 0.30 - - - - 0.00
1’55-5, ’2 ”0 .05‘ 50.. 20" ‘ - ' " ‘ .015
7120-20 10 030 11.71 3.52 1.52 - 0.11 - - - 0.50
0101-02 32 500 5.00 0.10 0.52 - 0.77 - - 0.01
0100-10 27 520 5.02 0.73 5.00 - - - - 0.13
0110-17 50 500 7.02 2.10 0.00 0.25 0.11 - - - 0.07
0130-0107 27 050 0.72 2.20 2.00 1.20 2.10 - - - 0.15
0110-21 20 770 7.10 2.33 1.07 2.05 0.03 - .00 - 0.11
1.000.. '4'1'2 “ET "SJT—TJT'z'TTc 1.72 0.“ 0.3? o 10 - 0.11
5103 20 500 7.33 7.00 - 0.00 - - - - 0.10
5111 35 770 17.30 17.05 0.13 - - - - - 0.21
5120 20 1000 0.03 0.00 0.02 1.01 ~ - 2.73 — 0.00
0112-13 20 050 2.02 1.02 - - 1.00 - - - 0.13
0125 17 050 21.02 20.02 - 0.00 - - - - -
7102-00 12 500 11.30 0.00 2.30 - - - - - 0.15
7117-10 00 030 3.00 2.31 0.30 0.07 - 0.10 0.00 - 0.10
7121-23 33 210 0.02 0.10 0.00 - - - - - 0.00
7120-25 15 330 2.30 1.32 - 0.00 - - - - 0.00
0100-00 0 500 5.00 0.10 2.70 2.70 - - - - -
0122-20 70 020 10.00 10.00 0.00 2.00 - 0.01 0 10 - 0.02
0100 22 020 30.10 20.05 1.23 0.05 - - - - 0.27
0110-10 10 000 03.50 0.01 2.10 50.30 - - - - 0.00
0127-20 10 1000 13.00 10.02 2.50 0.10 - - 0.00 - 0.31
10110-11 7 1000 20.20 17.00 10.50 0.00 - -‘ 0.10 - 0.0;
00.09. 010 000 15.55 0.05 1.00 0.20 0.11 0.00 0.31 - 0.10
0105-00 3 00 - - - - - - - - -
0112-13 15 70 0.17 - - - - 0.03 - — 0.10
0110-20 20 500 0.00 0.00 0.00 - 0.10 - - - -
0125-20 10 500 10. 10 10 . 10 - - - - - - -
5100 10 000 15.00 10.72 0.11 - 0.10 - - 0.10 0.31
5110-17 10 500 7.00 7.70 - - - - - - 0.21
5123 3 070 5.07 5.07 - - - - - - -
5131 s 000 .01‘ ’0“ " 50" ’ ' ' ' ‘
0120-7113 20 000 3.05 3.00 0.00 - - - - - 0.12
7120-20 13 000 0.77 0.05 1.50 - 7.51 - - - 0.25
0101-02 27 330 0.00 1.05 0.00 0.33 0.03 - - - 0.01
0100-10 20 500 0.03 0.03 - - - - - - 0.00
0110-17 22 550 0.02 1.02 0.30 0.23 0.17 - - - 0.03
0130-0107 0 750 12.03 3.00 1.03 1.11 7.00 - - - 0.05
0110-21 20 100 1.00 0.02 - 1.10 0.27 - - - 0.00
10001000 230 000 1.05
5103 00 730 22.50 21.05 - 0.10 0.02 - - 0.02 0.70
5110-11 00 070 20.00 20.05 0.00 0.00 - — - - 0.27
”1‘ ‘ 500 10.. 50., ' " ' ' .005 - "
0112-13 7 710 33.00 33.23 - 0.21 - - - - -
0125 15 730 10.00 10.77 0.13 - - - - - 0.01
7105 20 500 10.10 10.50 1.20 0.10 - - - - 0.10
7117-10 100 310 3.00 2.50 0.00 0.10 - - 0.00 - 0.07
7121-23 50 320 3.33 1.73 0.00 0.00 - - - 0.02 0.22
7120-25 23 570 0.50 0.73 3.00 0.75 - - - - 0.05
0100-10 10 700 20.20 0.11 1.00 15.20 - - - - -
0115-10 03 030 25.22 23. 73 0.00 0 .25 - - 0.00 - 0. 10
0122-20 00 070 20.07 21.00 0.05 0.52 - - - 0.01 0.00
0100-00 10 500 20.01 10.05 0.00 2.10 - - - - 0.01
0110-10 22 500 23.70 13.00 0.32 0.70 - - - - 0.05
0127-10105 10 500 7.23 1.07 1.00 3.00 - - - - 0.20
I” 501 500 17.02 13.00 0.70 2.77 0.00 - 0.01 0.00 0.12

001 00. at 0 - Chinook 01:0 0004
Inna n: Ill 11.: m m 9:! ml

 

 

 

2.10 - - - 2.10 - - - -
50” ‘ ' ‘ " - " ' 00..
5.03 ~ - - - - 5.03 - -
.0.’ - - ‘ ‘ .00: 00.1 " -
3.07 - - - - 3.07 0.00 — -
‘01. ' ’0’, ‘ 00‘. ' ' ' .033
5.01 - 5.03 - - - - - 0.00
5.35 - 3051 ’ " ‘ " ' .013
”0” ‘ 130‘! .0’7 ’ " ' - '
0.07 0.05 5.71 0.10 0.10 - - 0.03
‘0’! ‘0“ ‘0‘. .025 ' ‘ ' " 00.!
13.30 2.00 0.00 1.20 2.11 - 0.00 - 0.00
5.00 0.00 3.02 0.00 - - 0.00 - 0.11
0’ 0 0 0 0012 .05, ‘0‘, ° '0‘,
0.05 0.25 - 0.00 - - - -
:05. - ‘ ' ' ' ' ’01.
’0” .035 ’0’5 .01. " .00. .0.‘ ' .05,
5.50 1.03 0.07 - - - - - -
‘0“ .03. ‘01, 50“ " ' ' ' '0‘)
10.00 - 0.27 - - - 0.15 - 0.07
1‘0” 5011 '0‘, ’0.1 ‘ ' .053 ' .03.
33.00 20.57 3.00 1.10 - - - - 0.03
110” .0” 5011 ’90., ' - " ' .02.
150“ 50” ’0” .03. ‘ ’ .05. ‘ .03,
550., .0.’ ‘05. .0“ ' " .055 ‘ .0.’
5.30 - 5.37 - - - 0.01 - -
‘05 ’03; i0’i i0.’ " 00°; .0.‘ ’ .0”
’50.. ’0“ 1.0” ' 5.03. ’ ' ' '
0.02 0.01 - - - 0.10 - - 0.02
1.0.1 110‘. .0‘1 ’ .0‘1 ' ' - .0.)
0.25 0.52 - 0.50 0.32 - 0.50 - 0.20
2.37 0.15 - - 0.00 2.05 - 0.13
0.37 7.10 - 0.11 0.77 — 0.17 - 0.13
5.0“ .01. ’0“ .0“ " "' - ‘ .01‘
0.33 3.50 0.52 - - - - - 0.21
1,0,, .011 3055 ‘ 3‘02, ' " ‘ 50,1
’0‘, .02. .0.‘ ‘ 5031 ' " 00.1
11.01 1.01 0.75 - - - - 0.25
12.70 3.77 0.27 0.00 0.10 - - 0.12
10.23 2.00 3.30 1.07 2.57 - - - 0.17
’0’, 30" 20“ 30.5 .005 ' 00°! ’ .015
Iioi; ‘0’! 50‘; '0‘; [0.1 00.. .020 ' .0
12.50 12.11 - 0.10 - - - - 0.31
22.53 22.10 0.10 - - - - - 0.27
'0’, ‘0“ ‘0‘: 50.1 ' ‘ 10?, ‘ .00,
‘0’, )0” " " 03’ ’ ' ‘ .0”
310“ ’50.‘ ’ '0‘, " ' ' ' -
22.77 17.00 0.70 - - - - 0.30
7.03 5.32 0.00 1.07 - 0.23 0.00 - 0.01
0.30 0.00 3.27 - - - - - 0.20
0.00 3.00 - 2.00 - - - - 0.20
5503’ .0” ,0“ 5055 ‘ " ' " ’
10.07 13.02 5.70 - - 0.00 0.00 - 0.10
23.07 17.53 1.03 0.70 - 0.02 0.30 - 0.00
“01’ 3‘03. 50” ‘0': ' ’ " ' .03,
70.50 7.00 2.30 00.00 - - - - 0.07
13.00 10.02 2.50 0.10 - - 0.00 0.31
20.20 17.00 10.50 0.00 - - 0.10 0.00
20.00 2. .21 5.10 0.25 0.01 0.32 - 0.21
’0‘, ' ‘ ' ‘ .052 ‘ " 101.
10.07 10.07 0.11 - 0.10 - - - -
30.00 30.00 - - - - - - —
30.70 33.11 0.25 - 0.30 - - 0.30 0.70
‘50” 250“ ' ’ ' " ‘ ‘ ’0‘:
.0” .02. ' " - ‘ ' ‘ '
7.00 5.07 - 2.23 - - - - -
10,1 ‘0‘, 20" ' " ‘ ’ ° .0“
25037 .0” ’0’. " 1‘01? ‘ - ‘ .051
”0‘3. .03‘ 30” '0’, 120., ' - ' .001
13.07 12.07 - - - - - - 0.00
10.00 1.00 15.33 0.02 0.32 - - - 0.00
10.03 0.05 1.00 1.00 0.33 - - - 0.07
7.00 0.10 - 0.10 1.00 - - - 0.02

 
   

20.07
03.03
2.07
00.52
22.00
20.10
0.00
5.00
0.30
13.01
37.30
31.02
20.00
23.00
10 3.30
27.01 21.71

 

- 0.13 0.03 - - 0.03 1.01
.01: .0” ' ‘ "' " .0“
- - - - 0.10 - -

- 0.30 — - - - -

0.17 - - - - - 0.01
20‘. .0). " ' - ' .03,
2.20 0.07 - - 0.01 - 0.25
2.00 2.17 - — - 0.07 0.00
5.32 1.33 - - - - 0.00
2.70 21.77 - - - - -

00,1 .0), - ' 002. - .01.
0.07 0.73 - - - 0.01 0.00
5011 30., ‘ " - " 00.2
.0“ 5‘03; ‘ ‘ ‘ - '0'.
3.11 1.31 — — - - 0._5_3_
1.05 0.51 0.00 - 0.02 0.01 0.21

99

Table 9 . (cont 'd)

0020000 0! It '01 Int - All Chinook hroolt o! '01 In: - Chinook llth Food
memlEImummmm-nmllfimmmmmmml

 

 

 

 

 

 

 

 

 

 

 

 

W
0113 3 330 100.0 - - - 100.0 - - - - 100.0 - - - 100.0 - - - -
0125-20 0 130 100.0 - - - - - - - 100.0 100.0 - - - - - - - 100.0
5110-23 0 500 100.0 - - - - - 100.0 - - 100.0 - - - - - 100.0 - -
5131-0101 0 300 100.0 - - - - 70.0 23.1 - - 100.0 - - - - 70.0 23.1 -
0100-00 0 750 100.0 - - - - 00.0 0.1 - - 100.0 - - - - 00.0 0.1 - -
0113-10 11 010 100.0 - 03.1 - 10.0 - - - 0.0 100.0 - 03.1 - 10.0 - - - 0.0
0120-7113 21 700 100.0 - 01.0 - - - - - 0.2 100.0 - 01.0 - - - - - 0.2
7120-0/02 0 750 100.0 - 05.0 - - - - - 0.0 100.0 - 05.0 - - - - - 0.0
0100-10 0 700 100.0 - 02.2 7.0 - - - - - 100.0 - 02.2 7.0 - - - - -
0110-17 30 700 100.0 0.0 00.5 0.7 1.5 - - - 0.5 100.0 0.0 00.5 0.7 1.5 - - - 0.5
0130 15 000 100.0 23.0 72.1 0.0 - - - - 0.1 100.0 23.0 72.1 0.0 - - - - 0.1
0100-07 23 070 100.0 22.0 00.2 0.0 15.0 - 0.5 - 3.7 100.0 22.0 00.2 0.0 15.0 - 0.5 - 3.7
0120-21 20 000 __1_00.0 13.3 01.0 15.7 - - 1.5 - 2.1 100.0 13.3 07.0 15.7 - - 1.5 - 2.1
I” 100 000 100.0 7.0 00.0 0.5 5.1 2.5 0.0 - 3.7 100.0 0.1 03.0 0.1 5.0 2.0 12.0 - 5.0
5103-11 3 070 100.0 30.5 - 01.5 - - - - - 100.0 30.5 - 01.5 - - - - -
0112-7105 3 330 100.0 - - - - - - - 100.0 100.0 - - - - - - - 100.0
7117-10 50 520 100.0 10.5 75.3 5.0 - 0.0 2.1 - 0.2 100.0 10.5 75.3 5.0 - 0.0 2.1 - 0.2
7122-25 0 300 100.0 20.1 73.0 - - - - - - 100.0 20.1 73.0 - - - - - -
0100-00 0 750 100.0 3.1 00.2 21.0 - - - - 0.0 100.0 3.1 00.2 21.0 - - - - 0.0
.135‘3‘ ‘ 1“ 100.0 ' ’10, " ‘ ' 105 ' ‘0‘ 5..0. ‘ ’50, - ' ‘ ‘0, ' ‘0‘
0122-20 20 750 100.0 35.7 10.3 00.3 - - 3.0 - 2.1 100.0 35.7 10.3 00.3 - - 3.0 - 2.1
0100 10 700 100.0 00.0 11.0 3.3 - - - - 0.1 100.0 00.0 11.0 3.3 - - - - 0.1
0110-10 7 000 100.0 0.3 0.5 02.5 - - - - 0.7 100.0 0.3 0.5 02.5 - - - - 0.7
0127-20 0 750 100.0 12.0 01.1 2.0 - - 0.0 - 3.0 100.0 12.0 01.1 2.0 - - 0.0 - 3.0
10105-11 13 1000 100.0 05.0 10.0 2.0 - - 1.0 - 0.1 100.0 05.0 10.0 2.0 - - 1.0 - 0.1
10125 0 150 _mw - 00.0 _; - - 0.2 — - 100.0 - 00.0 - - - 0.2 - -
Am. 130 020 100.0 02.1 27.0 20.0 - 0.0 0.7 - 3.7 100.0 30.0 20.0 73.0 - 0.0 0.7 - 0.0
0/12-13 0 00 - - - - - - - - - - - - - - - - -
0110-20 0 250 100.0 7.1 50.7 - 3 .2 - - - 100.0 7.1 50.7 - 33.2 - - -
0125-20 02 200 100.0 00.0 - - 1.0 - - 0.2 100.0 00.0 - - - 1.0 - 0.2
5100 20 000 100.0 05.3 2.3 - 2.3 - - - 0.2 100.0 05.3 2.3 - 2.3 - - - 0.2
5110-17 30 300 100.0 50.0 - 1 .0 7.5 - 10.0 - 5.1 100.0 70.1 - 7.1 3.0 - 7.2 - 2.0
5123 10 000 100.0 0.0 - - 1.0 - 00.5 - 5.3 100.0 0.0 - - 1.0 - 00.5 - 5.3
5131-0101 03 010 100.0 05.0 - 1.3 0.2 - 2.0 - 1.0 100.0 05.0 - 1.3 0.2 - 2.0 - 1.0
0100-20 11 050 100.0 1.7 00.0 0.0 - - - - 1.3 100.0 1.7 00.0 0.0 - - - - 1.3
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0130-0107 27 050 100.0 20.0 20.0 31.0 20.0 - - - 1.0 100.0 20.0 20.0 31.0 20.0 - - - 1.0
0110-21 20 770 100.0 32.0 27.7 37.3 0.5 - 0.1 - 1.0 100.0 32.0 27.7 37.3 0.5 - 0.1 - 1.0
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5111 35 770 100.0 00.1 0.7 - - - - - 1.2 100.0 00.1 0.7 - - - - - 1.2
5120 20 1000 100.0 50.2 0.0 11.3 - - 30.0 - 1.0 100.0 50.2 0.0 11.3 - - 30.0 - 1.0
0112-13 20 050 100.0 57.3 - - 30.1 - - - 0.0 100.0 57.3 - - 30.1 - - - 0.0
0125 17 050 100.0 00.1 - 1.0 - - - - - 100.0 00.1 - 1.0 - - - - -
7102-00 12 500 100.0 77.7 21.0 - - - - - 1.3 100.0 77.7 21.0 - - - - - 1.3
7117-10 00 030 100.0 07.1 11.3 13.5 - 2.0 0.0 - 5.2 100.0 07.1 11.3 13.5 - 2.0 0.0 - 5.2
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0/22-20 70 020 100.0 70.0 0.3 20.1 - 0.1 1.3 - 0.2 100.0 70.0 0.3 20.1 - 0.1 1.3 - 0.2
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0127-20 10 1000 100.0 77.0 10.0 1.0 - - 0.0 - 2.3 100.0 77.0 10.0 1.0 - - 0.0 - 2.3
10110-11 7 1001 100.0 73.3 25.0 0.1 - - 0.5 - 1.1 _lflbJ 73.3 2_5.0 0.1 - — 0.5 1.1
0.100 010 000 100.0 00.0 10.0 20.2 0.7 0.0 1.0 - 0.0 100.0 01.7 10.3 20.3 1.2 0.1 1.5 - 1.0
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5100 10 000 100.0 05.2 0.7 - 1.0 - - 1.0 2.0 100.0 05.2 0.7 - 1.0 - - 1.0 2.0
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5123 3 070 100.0 100.0 - - - - - - - 100.0 100.0 - - - - - - -
5131 5 000 100.0 71.7 - 20.3 - - - - - 100.0 71.7 - 2 .3 - - - - -
0120-7113 20 000 100.0 03.7 13.0 - - - - - 3.3 100.0 03.7 13.0 - - - - - 3.3
7120-20 13 000 100.0 0.0 10.0 - 70.0 - - - 2.5 100.0 0.0 10. - 70.0 - - - 2.5
0101-02 27 330 100.0 21.3 10.5 0.0 50.2 - - 0.1 100.0 21.3 10.5 0.0 50.2 - - - 0.1
0100-10 20 500 100.0 00.1 - - - - - - 5.0 100.0 00.1 - - - - - - 5.0
0110-17 22 550 100.0 10.0 05.2 2.3 1.0 - - - 0.3 100.0 10.0 05.2 2.3 1.0 - - - 0.3
0130-0107 0 750 100.0 20.1 11.3 0.0 55.0 - - - 0.0 100.0 20.1 11.3 0.0 55.0 - - - 0.0
0110-21 20 100 100.0 1.3 - 00.2 1_0.2 - - - 0.3 100.0 1.3 - 00.2 10.2 - - - 0.3
I“ 230 31 100.0 00.7 12.0 5.0 20.0 0.0 - 0.1 1.0 100.0 00.0 11.0 5.0 10.1 0.1 - 0.2 2.0
5103 00 730 100.0 00.1 - 0.0 0.1 - - 0.1 3.3 100.0 00.1 - 0.0 0.1 - - 0.1 3.3
5110-11 00 070 100.0 00.0 0.3 2.0 - - - - 0.0 100.0 00.0 0.3 2.0 - - - - 0.0
5120 0 500 100.0 05.5 - - - - 0.5 - - 100.0 05.5 - - - - 0.5 - -
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0125 15 730 100.0 00.2 0.7 - - - - - 0.0 100.0 00.2 0.7 - - - - - 0.0
7105 20 500 100.0 00.2 7.7 1.2 - - - - 1.0 100.0 00.2 7.7 1.2 - - - - 1.0
7117-10 100 310 100.0 73.5 10.0 5.0 - - 0.1 - 2.0 100.0 70.0 17.0 3.0 - - 0.1 - 2.0
7121-23 50 320 100.0 51.0 20.0 20.0 - - 0.7 0.0 100.0 51.0 20.0 20.0 - - - 0.7 0.0
7120-25 23 570 100.0 55.0 35.2 0.0 - - - - 0.0 100.0 55.0 35.2 0.0 - - - - 0.0
0100-10 10 700 100.0 30.7 7.2 50.1 - - - - - 100.0 30.7 7.2 50.1 - - - - -
0115-10 03 030 100.0 00.1 3.0 1.0 - - 0.3 - 0.0 100.0 00.1 3.0 1.0 - - 0.3 - 0.0
0122-20 00 070 100.0 75.0 1.0 23.2 - - - 0.0 0.1 100.0 75.0 1.0 23.2 - - - 0.0 0.1
0100-00 10 500 100.0 00.2 0.0 10.0 - - - - 0.1 100.0 00.2 0.0 10.0 - - - - 0.1
0110-10 22 500 100.0 57.3 1.3 01.1 - - - - 0.2 100.0 57.3 1.3 01.1 - - - - 0.2
0127-10105 10 500 100.0 23.1 22.0 50.0 - - - - 3.7 100.0 23.1 22.0 50.0 - - - - 3.7
I” 501 500 100.0 70.1 0.0 15.7 0.0 - 0.1 0.0 0.7 100.0 77.0 5.2 10.2 0.0 - 0.1 0.0 0.0

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