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This is to certify that the

thesis entitled

The Effects of Low-head Lamprey Barrier Dams
on Stream Habitat and Fish Communities in
Tributaries of the Great Lakes

presented by

Hope R. Dodd

has been accepted towards fulfillment
of the requirements for

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1m c/CIRCIDdaDmpes-p."

THE EFFECTS OF LOW-HEAD LAMPREY BARRIER DAMS ON STREAM
HABITAT AND FISH COMhJUNITIES IN TRIBUTARIES OF THE GREAT LAKES

By

Hope R. Dodd

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

1 999

ABSTRACT

THE EFFECTS OF LOW-HEAD LAMPREY BARRIER DAMS ON STREAM
HABITAT AND FISH COMMUNITIES IN TRIBUTARIES OF THE GREAT LAKES

By

Hope R. Dodd

Low-head barrier dams are used to block adult sea lamprey (Petromyzon marinas)
from reaching suitable spawning habitat. However, these dams are suspected to have
several impacts on the stream fish communities. During the summer of 1996, twenty four
stream pairs were sampled across the Great Lakes basin with each pair consisting of a
stream with a low-head barrier and a nearby reference stream without a barrier. Barrier
streams were deeper and wider on average and contained more species than reference
streams. Barrier streams showed a peak in species richness directly downstream of the
dams and a sharp drop in species richness above the dams, indicating a blocking of fish
movement upstream. Barrier streams were more dissimilar in species composition
between above and below sections relative to reference streams, implying they do have a
minor impact on the fish community. Barrier effects on frequency of occurrence and
abundance of yellow perch, tout-perch, logperch and black bullheads were evident,
indicating their sensitivity to barriers. Rainbow trout (Oncorhynchus myksis) were
younger and grew faster in barrier streams, while white suckers (Catostomus
commersom) were older in barrier streams but grew at similar rates among stream types,

suggesting low-head dams are affecting the population dynamics of these two species.

Cepyn'ght by
Hope Rene’ Dodd
1999

To my family for their complete support and guidance.

iv

ACKNOWLEDGMENTS

The funding for this research project was made available by the Great Lakes
Fishery Commission. Extend thanks to the US. Fish and Wildlife Service, Department of
Fisheries and Oceans, and Ontario Ministry of Natural Resources for supplying valuable
information, advice, and technical support.

I would like to express my gratitude to Dr. Daniel B. Hayes for his guidance and
assistance in completing my degree. I would also like to thank Drs. J. Baylis, D. Noakes,
R. McLaughlin, L. Carl, R. Randall, the additional primary investigators, and J. Goldstein
and L. Porto, the graduate students working on this project. I also appreciate Drs.
Michael Jones and Richard Menitt for their advice and assistance in preparing my thesis.

Thanks to the graduate students in the Taylor/Hayes fisheries laboratory,
especially J oAnna Lessard, Jessica Mistak, Ann Krause, and Natalie Waddell-Rutter for
their help in data analysis and field work as well as emotional support. Thanks to all my
interns for assistance in the field and laboratory.

My deepest appreciation to my husband, Pete, for his patience, understanding, and
encouragement during my three year research study. A special thanks to my parents,
Jerry and Betty Clem, for their support and motivation throughout my academic career. I
would also like to thank Mr. Robert Windlan, my seventh grade biology teacher, who

gave me the desire to work hard and who sparked my interest in biology.

TABLE OF CONTENTS

LIST OF TABLES .............................................................................. vii
LIST OF FIGURES ............................................................................. viii
INTRODUCTION ................................................................................. 1
STUDY AREA .................................................................................... 5
METHODS ........................................................................................ 1 1
Field and Laboratory Methods ......................................................... 11
Data Analysis ............................................................................. 12
RESULTS .......................................................................................... 16
Habitat Analysis ......................................................................... 16
Fish Community Composition and Size Structure .................................... 19
Impacts on Individual Species ............................................................................ 35
Age and Growth Analysis .............................................................. 50
DISCUSSION .................................................................................... 68
CONCLUSIONS ................................................................................. 77
APPENDIX A ..................................................................................... 80
APPENDIX B ..................................................................................... 82
LITERATURE CITED ........................................................................... 86

vi

LIST OF TABLES

Table 1. Streams sampled in summer 1996 and re-sampled in summer 1997 (designated
by *). Note: stream pair 11 was not sampled and South Otter was used twice as a
reference stream. (Particle sizes: 1=clay, 2=silt, 3=sand, 4=gravel, 5=cobble,
6=bou1der,7=bedrock) ........................................................................... 6

Table 2. Total and (mean) number of species caught in above and below sections of
barrier and reference streams for summer 1996 and 1997 combined .................... 20

Table 3. Number of species caught in above and below sections of barrier and reference
streams (stream position) for summer 1996 and summer 1997 and average loss of
species upstream of the barrier (mean impact) .............................................. 21

Table 4. Mean community size composition and impact values for each stream pair for
1996 and 1997 combined ....................................................................... 36

Table 5. Number of streams in which each species were caught for the four stream
positions combining all streams and all years ............................................... 37

Table 6. Nmnber of sites in which each species were caught and impact values calculated
for the barrier stream (Banier Impact = (BA+BB)/(RA+RB)) and the barrier above

stream section (Above Impact = (BA/BB)/(RA/RB)). Missing values represent those
which could not be computed due to division by zero ...................................... 42

Table 7. Mean catch (+- one standard error) and mean loss of fish due to the barrier
(Impact = (BA-BB)-(R.A-RB)) for each species caught within the four stream
positions for all streams and years combined ............................................... 46

Table 8. Mean length for each stream position and loss of mean length above the barrier
(Impact = (BA-BBHRA—RB» for each species caught for all streams and all years

combined ......................................................................................... 51
Table 9. Number at age and mean age of rainbow trout for each stream (top table)

and for above and below sections (bottom table) ........................................... 55
Table 10. Number at age and mean age of white sucker for each stream .................. 61

Table 11. Number at age and mean age of white sucker for above and below
sections ............................................................................................ 62

Table 12. Comparisons between barrier and reference streams for age, growth, mortality,
and abundance of rainbow trout (top) and white suckers (bottom) ........................ 73

vii

LIST OF FIGURES

Figure 1. Photographs of low-head barriers in this study showing the “V” shape design
(top photograph) and the straight line design (bottom photograph) ......................... 3

Figure 2. Location of streams sampled in the Great Lakes Basin ............................. 9

Figure 3. Location of sites within a stream pair with a enlarged view of site 3 showing
the three transects ................................................................................. 10

Figure 4. Trends in mean width (top) and mean maximum depth (bottom) (+- one
standard error) for barrier and reference streams at the six sites sampled for all streams
and years combined .............................................................................. 17

Figure 5. Trends in mean particle size (top) and mean temperature (bottom) (+- one
standard error) for barrier and reference streams at the six sites sampled for all streams
and years combined .............................................................................. 18

Figure 6. Trends in total (top) and mean (bottom) species richness (+- one standard error)
for barrier and reference streams at the six sites sampled for all streams and years
combined .......................................................................................... 23

Figure 7. Trends in mean catch (top), mean area (middle), mean catch per area (bottom)
(+- one standard error) in barrier and reference streams at the six sites sampled for all
streams and years combined ....................................................................... 25

Figure 8. Influence of mean width (top) and mean maximum depth (bottom) on species
richness in barrier and reference streams combining summer 1996 and 1997 ........... 27

Figure 9. Influence of mean particle size (top) and mean temperature (bottom) on species
richness in barrier and reference streams combining summer 1996 and 1997 ........... 29

Figure 10. Influence of mean width (top) and mean maximum depth (bottom) on species
richness in each stream position combining summer 1996 and 1997 ..................... 30

Figure 11. Influence of mean width (top) and mean maximum depth (bottom) on loss of
species above the barrier (Impact) for 1996 and 1997 combined .......................... 32

Figure 12. Influence of barrier age (top), time of last breach (middle), and head height
(bottom) on loss of species above the barrier (Impact) for 1996 and 1997 combined...33

viii

Figure 13. Distribution of S¢rensen’s Similarity Index comparing composition between
the four stream positions (BA=Barrier Above, BB=Barrier Below, RA=Reference
Above, RB=Reference Below) ................................................................ 34

Figure 14. Regression of fish length on scale radius for back-calculations of lengths at
age for rainbow trout ............................................................................ 56

Figure 15. Growth of rainbow trout for East Branch AuGres/W est Branch Rifle pair (top)
and Miners/Harlow pair (bottom) ............................................................. 58

Figure 16. Catch curve and natural log transformed catch curve for rainbow trout for
East Branch AuGres/W est Branch Rifle stream pair ....................................... 59

Figure 17. Catch curve and natural log transformed catch curve for rainbow trout for
Miners/Harlow stream pair ..................................................................... 60

Figure 18. Regression of fish length on fin ray radius for back-calculations of length at
age for white sucker ............................................................................. 64

Figure 19. Growth of white sucker for East Branch AuGres/W est Branch Rifle pair (top)
and Miners/Harlow pair (bottom) ............................................................. 65

Figure 20. Growth of white sucker for West Whitefish/East Whitefish pair (top) and
Middle/Poplar pair (bottom) ................................................................... 66

Figure 21. Natural log transformed catch curves for white suckers for East Branch

AuGres/W est Branch Rifle pair (top), Miners/Harlow pair (middle), and Middle/Poplar
pair (bottom) ................................................. 67

ix

INTRODUCTION

The sea lamprey (Petromyzon marinas), a native of the Atlantic Ocean, invaded
the Great Lakes following the construction of the Welland Canal (Pearce et al. 1980). It
first appeared in Lake Erie in 1921 and soon spread to the upper Great Lakes (Applegate
and Smith 1951; Lawrie 1970). This parasitic species, along with substantial fishing
pressure, nearly eliminated native lake trout (Salvelinus namaycush) and populations of
other large commercial fish in the Great Lakes, resulting in the need for control of sea
lamprey (Lawrie 1970; Pearce et al. 1980; Smith and Tibbles 1980).

Since 1950, a variety of control methods have been instituted to reduce sea
lamprey abundance in the Great Lakes. Currently, there are several methods used to
control sea lamprey including chemical treatments, sterile male release, and construction
of low-head barrier darrrs. Chemical control with 3-trifluoromethyl-4wnitrophenol (TFM)
is the primary method utilized in Great Lakes tributaries. This lampricide targets the
larval stage of the life cycle by killing arnrnocoetes buried in the stream bed (Applegate et
al. 1957; Applegate et al. 1961; Hunn and Youngs 1980). Although TFM has little
apparent effect on fish species other than lampreys, public sentiment along with high cost
of chemical control has led the Great Lakes Fishery Commission to search for alternative
control methods to reduce the use of lampricides by 50% by the end of this decade (Great
Lakes Fishery Commission 1992).

To supplement chemical control methods, the sterile male release program has
been instituted on Lake Superior tributaries and in the St. Mary's River. This method of

control targets the spawning stage of the life cycle by releasing sterile adult males into the

population to mate with females, producing abnormal sea lamprey embryos that
eventually die. As the ratio of sterile males to normal males increases with consecutive
releases, spawning success will decline, thereby decreasing sea lamprey numbers
(Hanson 1981).

Another alternative to chemical treatment is the construction of barrier dams.
These dams are built to prevent adult sea lamprey from migrating to suitable spawning
habitat in Great Lakes tributaries. Early attempts at blocking spawning migrations
included installation of mechanical weirs and traps and the use of electrical barriers
(Applegate and Smith 1951; Smith and Tibbles 1980). These control methods were
deemed as ineffective, costly, and caused mortality to non-target species and most were
discontinued by the 1970s (Erkkila et al. 1956; McLain 1957; Dahl and McDonald 1980;
Hunn and Youngs 1980).

By the mid-19703, the Great Lakes Fishery Commission approved construction of
low-head barrier dams as part of the integrated sea lamprey control program (Hunn and
Youngs 1980). These dams range in height fiom approximately 60 to 300 cm with some
having a two-level tier and others having only one. They also vary in shape with some
having a “V” shape while others are build perpendicular to the stream (Figure 1). These
low-head barrier dams were built as a more effective control mechanism than mechanical
and electrical weirs while minimizing negative effects on non-target fish. Although low-
head barrier dams do not appear to cause direct mortality of non-target species, they can
have negative impacts at several different levels within the stream community (Pringle
1997). The most obvious impact is the blocking of fish movement during periods of

spawning or seasonal movement to locate suitable habitat and food resources. This

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Figure 1. Photographs of low-head barriers in this study showing the "V"
shape design (top photograph) and the straight line design (bottom
photograph).

limitation on movement may reduce species diversity, abundance and gene flow causing a
change in fish assemblage (Hunn and Youngs 1980; Pringle 1997). Low-head barriers
may also indirectly affect fish communities by changing the habitat (diversity and
substrate) and water quality (turbidity, temperature, and flow) of the stream (Ward and
Stanford 1983; Pringle 1997).

In this paper, I discuss the evidence for an impact of low-head lamprey barrier
dams on stream habitat and fish populations. My a priori hypothesis was that streams
containing low-head dams will contain fewer species and show a greater loss of species
upstream of the barrier when compared to upstream sections of nearby reference streams
(those without a barrier). I hypothesized that abundance of some non-target species will
decrease upstream of the dams due to habitat alteration or blocking of movement
upstream, thereby altering fish community and population size composition. Based on
previous studies of barrier dams and mechanical weirs, I postulated that the‘ population age
structure of white sucker (Catostomus commersom), a non-jumping migratory species,
would be skewed towards a younger age structure upstream of the dams and that growth
would be affected by the barriers due to the dam acting as a source of mortality by
allowing white suckers to traverse the barrier moving downstream but blocking movement
upstream. Age and growth of rainbow trout (Oncorhycus myksis), a jumping migratory
species, would not be affected by the barrier (Dahl and McDonald 1980; Hum and

Youngs 1980) because of their ability to pass the barrier in both the upstream and

downstream direction.

STUDY AREA

This project was a cooperative study between Michigan State University, the
University of Wisconsin — Madison, and the University of Guelph. Forty seven
tributaries were sampled across the Great Lakes basin in the summer (June-August) of
1996, and 14 streams were re-sarnpled in summer of 1997 (Table 1, Figure 2). For
sampling purposes, the streams in this study were divided among the three universities.
Streams were paired, with each pair containing a low-head barrier stream and a nearby
reference stream (without a barrier). Due to the lack of suitable reference streams, one
reference stream was used twice in the Lake Erie drainage. Stream pairs were selected
with the advice of sea lamprey control agents and technical experts. Reference streams
were selected based on proximity and similarity to the barrier stream in terms of stream
size, geology, and geography (Table l). The majority of streams were sampled at six
locations, three stream sites above and three below the barrier or a corresponding location
on the reference stream (Figure 3). However, some streams were sampled with fewer
sites when stream depth prevented safe sampling or the barrier was too close to the steam
mouth to allow placement of three sampling sites below the barrier. Site location was
primarily determined by access to streams with each site separated by at least 5-7 times
the stream width. We excluded from our sampling the small reservoir just upstream of
the barrier because water depth was too great to sample with our equipment. We also
excluded the plunge pool directly downstream of the barrier due to the potential for fish

to aggregate there unnaturally.

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10

METHODS

EieldandLathanMethods

Each sampling site contained a downstream, upstream, and middle transect. The
downstream transect was marked where the thalweg crossed the stream. The upstream
and downstream transect were separated by 5-7 times the stream width (Figure 3). A
middle transect was placed at approximately half the length of the site. At each transect,
stream width, maximum depth, and a pebble count of 50 stream bed particles were
measured to determine habitat characteristics. Pebble counts were taken by standing at
one side of the stream bank and walking along the transect. At each step, the observer
would reach down and determine the type of stream bed particle based on its size
(Kondolf and Li 1992). In addition to the habitat measurements mentioned above,
temperature and conductivity were also measured at time of sampling at the downstream
transect only to aide in setting the electroshocking unit.

In order to sample fish composition within a site, one pass with a backpack
electroshocker was made in an upstream direction with a zig-zag motion. This method is
generally adequate in providing species composition, richness, and relative abundance
(Simonson and Lyons 1995). Most fish were identified in the field and total length was
measured. Fish that could not be immediately identified were fixed in 10% formalin and
vouchered in 70% isopropyl alcohol for further identification in the laboratory.
Specimens that could not be identified due to their extremely small size or to damage

during transport and preservation were excluded in my analysis.

11

At time of fish measurement, rainbow trout scales were collected at a diagonal
between the posterior end of the dorsal fin and the anterior end of the anal fin above the
lateral line (Minard and Dye 1997). For white suckers, pectoral fin clips were taken
making certain at least the first three fin rays were collected. The right pectoral fin was
used when possible.

In the laboratory, scales were mounted between two glass slides for reading
purposes. White sucker fin rays were embedded in epoxy, sectioned using a diamond
blade saw, and mounted between glass slides (Scidmore and Glass 1953; Beamish and
Harvey 1969). Glycerin was used as a clearing agent to aide in reading fin rays. To age
and measure length of scales and fin rays, an Optimas imaging system was used.
12W

For data analysis, sites were combined into above and below stream sections.
An or value (Type I error) of 0.05 was used for all statistical tests. To determine
differences in width, maximum depth, particle type, and water temperature between
barrier and reference streams, a nested mixed model analysis of variance (AN OVA)
design was used treating stream pair, stream, and position (Above or Below) within each
stream as random effects and stream type as the fixed effect. The relationship between
stream habitat characteristics and species richness was examined with a nested mixed
model analysis of covariance (ANCOVA) design again using pair, stream, and position as
random effects and stream type as a fixed effect to compare differences in barrier and
reference streams. For comparing differences in species richness among the above and

below sections of barrier and reference streams and relating these differences to habitat, I

12

also used a nested mixed model ANCOVA with pair and stream as random effects and
stream position as the fixed effect. I estimated an average loss of species (impact value)
due to the barrier using the formula:
I=(BA-BB)-(RA-RB), [1]
where I is the impact value for a stream pair and where all other variables refer to species
richness within a stream position for a stream pair (BA = Barrier Above, BB = Barrier
Below, RA = Reference Above, and RB = Reference Below). A two-tailed t-test was used
to compare the observed impact to the expected impact of zero. In order to examine
habitat influences on the number of species lost above the dams, regressions of average
width and maximum depth were performed on loss of species calculated for each stream
pair. The influence of age, time of last breach, and height of the dams on loss of species
were also examined through regression analysis.
To determine impacts of barriers on fish community composition, Sprensen's
similarity index (S¢rensen 1948) was computed between stream sections
QS = 2C / (A + B), [2]
where QS is the index of community similarity, A is the number of species in one stream
section, B is the number of species in the second stream section, and C is the number of
species common to both stream sections. A Tukey's Studentized Range test was then
used to evaluate differences between similarity indices. Similar to the calculation of an
impact value for species richness, I estimated an average loss of fish community size (i. e.

average length of all fish combined) above low-head barriers by substituting mean

13

community size for richness in equation [1] and performed a two-tailed t-test to indicate
differences in mean length due to the barrier.

Sensitivity of particular species to barriers was based on comparisons of
frequency of occurrence, mean catch, and mean length for above and below sections of
barrier and reference streams. For frequency of occurrence, two impact ratios were
computed. The Barrier Impact compared frequency of occurrence between the barrier and
reference stream, and the Above Impact compared the barrier above section with that of
the reference stream. The Barrier Impact and Above Impact ratios for frequency of
occurrence were calculated using the formulas:

131,",q = (BA+BB) / (RA+RB), [3]

AIfreq = (BA/BB) / (RA/RB) [4]
where BI is the Barrier Impact ratio, A1 is the Above Impact ratio, and where all other
variables refer to the number of sites a particular species was found within a stream
position (BA = Barrier Above, BB = Barrier Below, RA = Reference Above, and RB =
Reference Below). The Impact score for both mean catch and mean length was
calculated using equation [1], substituting mean catch or mean length for richness.
Species were considered sensitive to barriers based on their magnitude of their Impact
ratios and Impact scores.

Differences in age between stream types and stream positions were determined by
performing a mixed model ANOVA on mean age for both rainbow trout and white
sucker. For growth analysis of rainbow trout and white sucker, the Hile method (a
modified version of the F raser-Lee method) of linear regression was used to compute

length of the fish at scale (or fin ray) formation and back-calculations of lengths at age

14

were computed (Francis 1990). From the back-calculated lengths at age, incremental
growth for the previous year was calculated and previous length at age was regressed on
incremental growth for each stream sampled. A mixed model AN COVA was used to
determine differences in the growth between barrier and reference streams by testing the
slopes of the two regression lines for homogeneity. Catch curves were constructed for
each stream and differences in instantaneous mortality rate (i.e. the slope of the
regression) between barrier and reference streams for the two species was ascertained
through an ANCOVA analysis. For age, growth, and mortality analyses, stream pair was
treated as a random effect, and stream type and stream position were considered fixed
effects. Rainbow trout structures were collected from two stream pairs, but the Miners
and Harlow pair was removed from the analysis on instantaneous mortality due to a low
number of age structures collected in Miners River. White sucker fin rays were collected
and aged from four stream pairs. The West Whitefish/East Whitefish pair was excluded

in the analysis of mortality rates due to the lack of white suckers older than age two in the

East Whitefish River.

15

RESULTS

H l . l l .

Most streams in this study were cool water tributaries to the Great Lakes. Both
barrier and reference streams ranged widely in size (Table 1). Streams with low-head
barriers had an average width of 11.0 m and an average maximum depth of 65.4 cm while
the mean width and maximum depth for reference streams was 9.4 m and 52.2 cm.
Barrier streams were significantly wider and deeper than reference streams (Pm=0.023 6,
PM = 0.0018) with a difference in mean width of 1.9 m and mean maximum depth of
13.9 cm. Average particle size for both barrier and reference streams was gravel with no
significant difference in predominant substrate type between stream types (P=0.999).
Mean water temperature for barrier streams was 17.5 °C and for reference streams was
18.1 °C with no significant difference between stream types (P=0.9027).

To further study habitat alteration by barrier dams, we calculated mean width,
maximum depth, particle size, and temperature at the six sites sampled in reference and
barrier streams. Average width and maximum depth gradually increased in a downstream
direction for both stream types, however, barrier streams were generally wider and deeper
at all sites (Figure 4). At sites just upstream of the dams, mean maximum depth was on
average 15 cm greater than in the reference streams, suggesting that some effect of the
impoundment extended upstream to these sites. Mean particle size and temperature were
similar among sites for barrier and reference streams, although streams without dams
tended to have slightly higher temperatures at all sites (Figure 5). Unlike width and

depth, mean particle size and temperature did not show a downstream trend.

l6

16~
14«
124
10~
8.
64
4-

   

+ Barrier

Mean Width (m)

- i - Reference

 

O
_<
_l
_.1
.4

 

3 2 1 Barrier 1 2 3

¥,/‘I\‘f

 

+ Barrier

Mean Maximum Depth (cm)
8

— I - Reference

 

 

3 2 1 Barrier 1 2 3

Figure 4. Trends in mean width (top) and mean maximum depth (bottom)
(+- one standard error) for barrier and reference streams at the six sites
sampled for all streams and years combined.

17

1 =clay

 

 

 

 

8 2=Silt
l =sand
7 “ 4=gravel
o 6 . . 5=cobble
g 6=boulder
5 ~ ..
% 7-bedrock
g 4 . m N34
0..
c 3 -
8 .
2 2 0 + Bamer
1 . — a- Reference
0 . j
3 2 1 Barrier 1 2 3
Abram Below
20.0 7
" 17.5 - ,. N
8
e
.3
g 15.0 «
g +83rrier
: 12-5 ‘ - I- Reference
8
2
10.0 r

3 2 1 Barrier 1 2 3
Aboxe Belem

Figure 5. Trends in mean particle size (top) and mean temperature
(bottom) (+- one standard error) for barrier and reference streams at the
six sites sampled for all streams and years combined.

18

Overall, barrier streams contained a greater number of species than reference
streams. A total of 14 and an average of 3.8 more species were caught in barrier streams
compared to reference streams with higher species richness occurring in both above and
below sections of barrier streams (Table 2). Difference in average richness was greater
between the below sections of barrier and reference streams (3.8 species) when compared
to that of the above sections (0.7 species). Moving upstream within a stream type, total
and average species richness declined by 20 and 4.7 species in barrier streams, while in
reference streams, total richness decreased by 14 species and average richness declined
by 1.6 species.

There was little difference in average species richness between summer 1996 and
1997 among above and below sections of barrier and reference streams (Table 3).
Average richness for the 24 barrier streams sampled in 1996 was 12.7 and for the seven
re-sarnpled in 1997 was 11.2 species. Reference streams contained fewer species on
average with 10.6 species in 1996 and 9.9 species in 1997. Comparing just those seven
stream pairs that were sampled in both years, the barrier above sections differed by an
average of 0.1 species and the barrier below differed by 2.1 species. Reference streams
showed a difference in average richness of 0.9 species above and 1.8 species below

between years.

To detect patterns in richness and associate those patterns with habitat differences

between barrier and reference streams, I examined species richness at the site level. For
reference streams, both total and average species richness generally increased in a

downstream direction with the exception of the Above 1 and Below 2 sites (Figure 6).

l9

Table 2. Total (top table) and mean (bottom table) number of species
caught in above and below sections of barrier and reference streams for

summer 1996 and 1997 combined.

 

 

 

 

 

Barrier Reference
Above 54 48
Below 74 62
Total 79 65
Barrier Reference
Above 1 1 .3 10.6
Below 16.0 12.2
Total 18.6 14.8

 

20

 

 

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30 ~

Total Species Richness

- I - Reference

 

 

20 f 0

4 4 —0— Barrier

Mean Species Richness
\
l
I
I
m
I
I
11"
\
\

2 ~ - I- Reference

 

 

3 2 1 Barrier 1 2 3
Am Below

Figure 6. Trends in total (top) and mean (bottom) species richness (+- one
standard error) for barrier and reference streams at the six sites sampled
for all streams and years combined.

23

For barrier streams, a different pattern was apparent. Within barrier streams, above sites
were similar in terms of total and average species richness although total richness shows a
small decline towards the darn. However, the highest total and mean richness was seen at
the site directly below the dam (Below 1) compared to all other sites. Barrier streams
exhibited a distinct peak in mean richness of 10.8 species that then declined toward the
mouth while reference streams showed a gradual increase downstream. Comparing
barrier and reference streams, the above sites were more similar in both total and mean
richness than below sites.

Due to the high peak in richness directly downstream of the dam, average catch at
each site was computed across barrier and reference streams to detect influences of the
dam on the relative fish abundance. The pattern seen for mean catch differed fiom that of
average richness particularly for reference streams (Figure 7). In reference streams, mean
catch increased towards the hypothetical barrier where it peaked directly below the
hypothetical dam and then declined further downstream, but the average richness in
reference streams showed a gradual increase from above to below sections. The mean
catch in above sites of barrier streams show a trend opposite to that of reference streams
with a decline in mean catch toward the darn. Both barrier and reference streams
demonstrate a large number of fish caught at the site directly below the barrier (or
hypothetical barrier) that then decreases rapidly in a downstream direction. However, the
difference in mean catch traversing the barrier (i.e. from Below 1 to Above 1) is greater
(35.8 fish) than traversing the hypothetical barrier (6.9 fish). Due to barrier streams being
wider on average than reference streams, I took into account the area of the stream

sampled at the six sites for barrier and references streams and computed a catch per area

24

80 l
70 0
60 ~
50 -
40 0
30 ~
20

+ Barrier

- I — Reference

Mean Catch

 

 

10001
900 J
800 ~
700 4
600 a
500 —
4001
300 -
200

 

Mean Area (m2)

—0— Barrier

} - I — Reference

 

0.4 —

0.3 _ + Bamer

- I - Reference
0.2 ~

0.1 ~

 

Catch Per Area (CPA)

 

 

Figure 7. Trends in mean catch (top), mean area (middle), and mean catch
per area (bottom) (+- one standard error) in barrier and reference streams
at the six sites sampled for all streams and years combined.

25

(CPA). For both stream types, mean area generally increased in a downstream direction,
but was larger at all sites in barrier streams. Comparing barrier and reference streams,
above sites were more similar in mean area than below sites with the largest differences
in mean area between stream types being at the Below 1 (235.4 m2) and the Below 3 sites
(322.1 m2). By taking into account area when examining mean catch, I found that the
Below 1 sites which had the highest mean catch for both stream types had a relatively
small catch per area compared to all other sites. In both barrier and reference streams,
catch per area generally declined in a downstream direction with reference streams having
higher CPA at all sites except the Below 2 site. However, barrier streams were more
similar in CPA across sites compared to reference streams which varied more widely.
Since stream width and depth differed significantly between barrier and reference
streams, I examined the possibility of these habitat characteristics explaining the
differences seen in average species richness and average catch. I first tested the
relationship between the two habitat characteristics and species richness to determine if
the slopes were heterogeneous between barrier and reference streams in terms of species
richness (Figure 8). This analysis indicated that the slopes of the lines for barrier and
reference streams were not significantly different from each other (P=0.8177). Because
the slopes were similar, an AN COVA analysis was then performed on differences in
species richness between barrier and reference streams where the slopes were restricted to
be equal (i.e. without interactions). The results of this test indicated that average species
richness was significantly different between the two stream types (Pm =0.0334) with
width and depth being significant covariates (Pwidth =0.0046, Pm=0'0091)- Although

stream bed particle size and water temperature were not significantly different between

26

Species Richness (numbers)

Species Richness (numbers)

 

    
 

 

 

 
   

 

30 0 Barrier
o I Reference
25 ~
20 « ° 0 0 Barrier
. ’ Q .(
I
15 ' . . I 09' . I
I I _I ._I —-
10 - __ '— 31. ° K Reference
I I I I
5 — l = 0 II I
‘ O
0 I I I I l
0 5 10 15 20 25
Mean Width (m)
30 o Barrier
. I Reference
25
20 _ . . 0 Barrier
I O. O O . .0 K
15 0
a. -
o t I : co \- o
5 “ ~ . ° 'Rfierence
I O O
0 ji 1 I I I I I *I
0 20 40 60 80 100 120 140 160

Mean Maximum Depth (cm)

Figure 8. Influence of mean width (top) and mean maximum depth (bottom)
on species richness in barrier and reference streams combining
summer 1996 and 1997.

27

barrier and reference streams, I regressed these habitat variables against mean richness to
determine possible influences on number of species caught and found that particle size
and temperature could not explain the differences in species richness between stream
types (Figure 9). For mean catch, I also used a slope heterogeneity test to determine the
influence of width and depth on relative abundance (i.e. mean catch). From the

AN COVA, I determined that the slopes for barrier and reference streams were
heterogeneous with mean width and all interactions being significant (Pwidm=0.001,
Pwidmwfif 0.0248, Pdepm.b,,,,-,,=0.0386, P000~000=000120 Pfim.d,pmm=0.0215).

A slope heterogeneity test was also used to examine differences in species
richness among above and below sections of barrier and reference streams (the four
stream positions) that may be attributable to stream width and depth (Figure 10). The
slopes of the lines were not significantly different from each other, indicating similar
slopes between stream positions (P=0.4649). An AN COVA performed on species
richness where all four slopes were forced to be equal showed significant differences in
average richness between the four stream positions (Pm =0.0334) with differences
between the above and below barrier sections (BA vs. BB, P=0.001) and the below
sections of barrier and reference streams (BB vs. RB, P=0.0057) being significant. In this
analysis, stream width was the only significant covariate (Pm=0.0219).

I further examined the effect of low-head barrier dams on species richness by
calculating a loss of species above the dam (impact values) for each stream pair. On
average, barrier streams lost 4.04 species fiom below to above segments while reference
streams lost only 1.52 species. The overall impact of the barriers on species richness was

a decline of 2.52 species above the dam relative to reference streams (Table 3). This loss

28

3° 1 0 Barrier

25 q I Reference
20 - ° 0

o
0"
I

$ . Barrier
.' .r /

1° ‘ *3 H t . v\Reference

   

Species Richness (numbers)
a."
o

 

 

.1

Mean Particle Size

0 Barrier
200
18 J I R rence o I Reference
16 ~
14 -
12 ~
10 ~
8 _
6 _
4 -
2 _

 

 

Species Richness (numbers)

 

Mean Temperature (°C)

Figure 9. Influence of mean particle size (top) and mean temperautre

(bottom) on species richness in barrier and reference streams combining
summer 1996 and 1997.

29

30 1 o Barrier Above (BA)

 

 

 

 

I I Barrier Below (BB)

g 25 “ A Reference Above (RA)
8 . 33 x Reference Below (RB)
g 20 ~

I?

2 15 ~

.C

5:3

0 10 —

.93

0 f I F T I
0 5 10 15 20 25
Mean Stream Width (m)
30 _ o Barrier Above (BA)
I Barrier Below (BB)

.. ' AReference Above (RA)
E 25 ‘ XReference Below (RB)
8

a 20 _
5 BB

1 15 -
.C
3:3
3 10 —
O I I I f T I I I

 

 

0 20 40 60 80 100 120 140 1 60

Mean Maximum Depth (cm)

Figure 10. Influence of mean width (top) and mean maximum depth (bottom)
on species richness in each stream position combining summer 1996 and 1997.

30

of species was significantly different from our expected value of zero under the null
hypothesis of no impact on species richness by low-head dams (P= 0.0126). Although the
distribution of impact values across the stream pairs were not normally distributed
according to the Shapiro-Wilk normality test (W = 0.909949, P=0.0346), the boot strap
method found that this significant difference in average impact score was robust. I
explored the effect of habitat on the degree of species decline upstream through
regressions of mean width and mean maximum depth on loss of species (i.e. impact).
These regressions were not significant (Pwm=0.4194, Pdepm=0.7535) and showed
substantial scattering of the data (Figure 11).

In this study, low-head barriers differed in terms of age, shape, height, and size of
the impoundment. Location of barriers upstream of the mouth also varied between
streams. Dams ranged in age from 2 to 26 years and in height from 20 to 430 cm. I
analyzed the possible influence barrier characteristics may have on decline in species
upstream of the darn by regressing barrier age, time of last breach, and head height on
loss of species (Figure 12). I found that none of these characteristics were good
predictors of species loss above low-head dams (P,g,=0.7952, Pm¢h=0.293 8,
Pmiw=0.7175).

S¢rensen’s similarity index based on species presence/absence data was computed
to compare fish community composition between above and below sections of barrier and
reference streams. The highest similarity in species composition was within reference
streams with a mean index value- of 0.68 (Figure 13). Barrier streams were found to be

the second highest in mean similarity of species composition. Comparing above and

31

 

 

 

 

 

o o
2 ~ 00
A 0 o o o
g 0 « e
00
g -2 a 0 ° o
g -4 ~ 9
o o
B -6 — °
0) 0
‘.<5 -8 ~ 0
m
m
3 '10 ‘ 0 . y = 0.1574x - 4.2526
-12 - R2 = 0.0244
0
'14 T I r 1 I
0 5 10 15 20 25
Mean Width (m)
5 -
3 — o o o .
T5 1 — o o o e
8 1 O o 0
.§ ' ‘ 0 #—
2): -3 - 7 . . o
g -5 « . 00
a) -7 - 0
.._ o
o -9 _
3 ° 0
3 '11 a y = 0.0171x - 3.6383
'13 ~ ° R2 = 0.0052
'15 I r r I f l
0 20 40 60 80 100 120

Mean Maximum Depth (cm)

Figure 11. Influence of mean width (top) and mean maximum depth

(bottom) on loss of species above the barrier (Impact) for 1996 and 1997
combined.

32

 

 

 

 

 

 

 

 

 

7;; 5 .

Q . o e .

E o o o o o

5 0 4 ° 0 o

8 “fl—

.8 _5 fl 0 e . o

O. O

33 40 - . 0 y=—0.0404x-1.9616
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8 -15

4 I l j T I l

0 5 10 15 20 25 30
Age of Barrier (years)
‘3
5 -

a . . ,

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a c 4* °

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a, 10 ° . 0 y = -0.1699x - 0.808
- ' ‘ O

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g '15 I I I I I I I
" 0 5 10 15 20 25 30

Time of Last Breach (years)
5 5 I
o

g- 0 - ° .00 .3.

'72“ —-—‘ °

.3 o

6 -5 ~ 0 O o

8 o

a) c

“5 -10 - . . y = -0.0039x - 2.1557
g . R2 = 0.0061

-' -15 . , r r .

0 100 200 300 400 500
Head Height (cm)

Figure 12. Influence of barrier age (top), time of last breach (middle) and
head height (bottom) on loss of species above the barrier (Impact) for
1996 and 1997 combined.

33

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P L _ _ o
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34

below sections between stream types, the below stream sections were more similar in
species composition (0.57) than the above sections (0.53), although previously we found
differences in total and mean species richness was shown to be greatest between the
below sections (Table 2). A Tukey’s Studentized Range test performed on mean
similarities indicated the principal difference was between the highest (within reference
stream) and lowest (between above sections) similarities only (P=0.0249).

Differences in mean fish community size composition between barrier and
reference streams were determined by calculation of an impact value for each stream pair.
In barrier streams, community size composition differed by 6.05 mm between above and
below sections while reference streams showed a slightly smaller difference of 4. 12 m
(Table 4). Overall, the fish community above the barrier was 1.86 mm smaller relative to
the reference stream and was not significantly different from our expectation of zero
under the null hypothesis of no effect (P=0.7302).

For each species, frequency of occurrence was calculated and two impact scores
were computed for each to assess their sensitivity to low-head barrier dams. The Barrier
Impact score identifies species which were caught more fiequently in barrier (> 1) versus
reference streams (< 1), indicating a whole system impact of the barrier. An Above
Impact score identifies species which were found more (> 1) or less (< 1) often above the
barrier dams, indicating an upstream impact of the dam. Based on frequency of
occurrence data, the five species with the widest distribution (i.e. found in the most
number of stream sections) were creek chub, mottled sculpin, blacknose dace, longnose

dace, and rainbow trout (Table 5). These species did not appear to be impacted by the

35

Table 4. Mean community size composition and impact values for each stream

pair for 1996 and 1997 combined.

 

 

Stream Barrier Barrier Reference Reference
Pair Above Below Above Below
1 85.00 87.04 77.48 81 .40
2 61 .85 75.77 64.97 66.43
3 62.94 67.28 72.00 66.81
4 69.96 67.12 69.52 67.47
5 73.97 63.79 68.57 54.67
6 68.41 82.87 68.90 82.38
7 78.42 92.13 101.58 122.05
8 91.77 96.53 87.83 132.31
9 60.39 123.75 50.42 83.92
10 68.42 78.98 88.17 75.30
12 78.68 69.56 77.68 100.21
13 73.01 69.78 80.01 57.56
14 58.46 73.39 62.76 55.78
15 72.89 71 .86 67.44 69.68
16 73.72 67.03 59.49 51.41
17 79.98 87.25 78.53 81.28
18 65.80 55.57 61.40 58.12
19 36.22 85.85 65.56 78.80
20 149.80 81.23 76.86 91.19
21 80.48 80.23 65.56 78.80
22 62.28 86.36 57.15 56.38
23 90.94 72.02 93.91 80.50
24 61.58 78.20 69.58 73.77
25 86.83 123.53 62.57 62.29 _
Mean 74.66 80.71 72.00 76.19

36

 

Mean
Im act

1.88
-12.45
-9.53
0.79
-3.71
-0.98
6.76
39.72
-29.86
-23.42
31 .65
-19.22
-21.91
3.28
-1 .38
-4.53
6.95
-36.39
82.90
13.49
-24.84
5.51
-12.42

-36.98

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dam in terms of the number of sites in which they were caught (Table 6). Several species
did appear to be negatively impacted by the barrier. Sea lamprey, yellow perch, and
trout-perch were not caught above the dam in any of the study streams, but sea lamprey
and trout-perch were captured more frequently in barrier streams as indicated by their
Barrier Impact ratios (1.11 and 1.25, respectively) (Table 6). Northern pike, largemouth
bass, and logperch were seen less frequently in the above barrier sites relative to the other
three stream sections with northern pike and largemouth bass showing higher occurrence
overall in barrier streams (Barrier Impact = 1.09 and 2.00, respectively) while logperch
showed a slightly higher occurrence in reference streams (Barrier Impact = 0.82). Other
fish species appeared to be positively impacted by the barrier (i.e. seen more fi'equently in
above sections of barrier streams). Blacknose Shiner, brassy minnow, american brook
lamprey, and northern brook lamprey were caught more fiequently in barrier streams
particularly in sites above the dams. Black bullhead were also found more often above
the barrier relative to the reference stream (Above Impact = 2.67), but occurred equally as
frequent in barrier and reference streams as a whole (Barrier Impact—‘1 .00).

As with frequency of occurrence data, mean catch in each stream position and
decline in mean catch (i.e. Impact) was computed for each species (Table 7). For this
impact score, a negative value indicates a loss in mean catch while a positive score shows
a gain in number of fish upstream of the darn. Although their frequencies were not
affected by the dams, mean catch of longnose dace and central mudminnow, two of the
most widely distributed species, showed a decline in catch above barrier dams (-3.5 7 and
-O.87, respectively). Logperch, a species which occurred less often in the above section of

barrier streams, also declined in numbers above barriers on average relative to reference

41

 

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49

streams (-0.67). However, other species were found to have a higher mean catch
upstream of the dams. Black bullhead were not only found more often above barriers but
were greater in mean catch as well (1.66). Another species with higher mean catch
upstream of the dams was slimy sculpin with an impact score of 0.50. Mean length was
also tabulated for each species. However, high variability among fish lengths did not
allow a clear pattern to be detected for any individual species (Table 8).
AgmdfimmhAnalxsis

Rainbow trout ranged in age from zero to three years for all four streams sampled
with most fish being young of the year (age zero) (Table 9). Age four and five rainbow
trout were caught but excluded from the analysis due to these fish being lake nm
steelhead which were not a part of the stream community during the time of this study.
Mean age ranged from 0.2 to 1.0 years with rainbow trout being significantly older on
average in reference streams compared to ban'ier streams (P=0.0016). For the East
Branch AuGres/W est Branch Rifle pair, mean age of rainbow trout was higher in the
above sections while, in the Miners/Harlow pair, mean age was lower in above sections.
Taking into account both stream pairs, I found a significant difference among the four
stream positions (P=0.0001). Rainbow trout in the above section of barrier streams were
significantly older than those in the below section by approximately 0.5 years
(P=0.0005). There was also a significant difference between the below sections of barrier
and reference streams with the reference below section containing older rainbow trout
(P=0.0001).

For grth analysis of rainbow trout, a regression of fish length on scale radius

was used to determine the length at which scale formation occurred (Figure 14). The x -

50

 

 

 

 

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52

 

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53

 

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54

 

 

 

 

 

 

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55

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56

intercept value was then used to back-calculate the length at annulus formation for the
year in which the fish was caught and the previous year. Incremental grth for that year
was then computed by taking the difference between the two back-calculated lengths to
find the growth of the individual fish for the previous year. An AN COVA was performed
on the regressions of previous length at age and incremental growth to examine
differences in grth for the previous year between stream types (Figure 15). Based on
the analysis, rainbow trout in barrier streams demonstrated significantly higher grth
(approximately 10 mm) than in reference streams (P=0.0017).

Catch curves were constructed for all four streams to examine differences in
mortality of rainbow trout among stream types. Based on the catch curves, rainbow trout
appeared to be fully selected by the backpack electroshocker at age one, therefore, age
zero fish were dropped from the analysis (Figure 16, Figure 17). Since I caught only two
fish in Miners River that were older than age zero, I excluded the Miners/Harlow pair
from this analysis. The catch curves were log transformed such that I could test for
differences in instantaneous mortality rate (i.e. slope of the line). Results from the
AN COVA, indicate there was no significant difference in mortality between the barrier
and reference stream (P=0.3205).

White suckers showed a much broader age range from age zero to twelve for all
streams sampled with most fish being age one (Table 10, Table 11). Mean age ranged
from 1.00 to 3.90 years with white suckers being significantly older in barrier streams by
approximately 0.4 years (P=0.0480). Within each reference stream, mean age of white
sucker was similar between above and below sections except for the Poplar River in

which mean age was higher in the above section. Mean age for barrier streams was

57

140 0 East Branch AuGres

 

 

 

 

 

 

 

120 y = -0.1384x + 82.63
E E. AuGres I West Branch Rifle
E y = —0.2947x + 88.122
2
(D
5 ‘6
C
‘2’ ---.-°
g
_:_ W. Rifle
20 ~
0 I T r T I Y Y —1
o 20 4o 60 80 100 120 140 160
Previous Length at Age (mm)
160 o Miners
y = 0.0875x + 104.66
14° Miners I Harlow
.5 120 v” y = -0.1167x + 76.728
g #2
g 100
<3 so _ '
£9 ____________________ I
so *
g Harlow
I
5 4o .
20 -
0 I I 1 j
o 20 4o 60 80 100

Previous Length at Age (mm)

Figure 15. Growth of rainbow trout for East Branch AuGres/ West Branch
Rifle pair (top) and Miners/Harlow pair (bottom).

58

 

 

—-O— East Branch AuGres

— I - West Branch Rifle

 

  
 

 

 

if?
8
8
E
3
z
0 2 3 4
Age (years)

4.0 ~ 0 East Branch AuGres
'8 3.5 _ y = -1.4311x + 4.8756
‘3 I West Branch Rifle
8 3'0 ‘ y = -1.0986x + 3.3917
" 2.5 -
3 E. AuGres
g k
g 2.0 — \

1.5 .
§’
3 1.0 —
.3 W. Rifle
z 0.5 < \

0.0 T B. n

0 2 3 4
Age (years)

Figure 16. Catch curve and natural log transformed catch curve for rainbow
trout for East Branch AuGresNVest Branch Rifle stream pair.

59

—O— Miners

 

 

 

 

 

 

- I- Harlow
8
‘6
9
B
‘3
B
E
3
z
0 1 2 3 4
Age (years)
8 3.5 a oMiners
*5 '\ y = 0
g 3 7 \ I Harlow
o
O = -
5 2.5 ~ \ "mow y 2.2336x + 5.5658
‘6 2 ~ \
2 1 \
“5 5 ‘ \
§’ 1~ -
E .
§ 0'5 Miners
2 0 ¢ : . fl
0 1 2 3 4
Age (years)

Figure 17. Catch curve and natural log transformed catch curve for rainbow
trout for Miners/Harlow stream pair.

60

 

 

 

 

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61

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62

highest in above sections of the East Branch AuGres and West Whitefish, while the other
two barrier streams (Miners and Middle) showed older white suckers in the below
sections. Taking into account all stream pairs, I found a significant difference in mean
age among the four stream positions (P=0.0017). White suckers above barrier dams were
significantly younger than those in the below section by approximately 0.7 years
(P=0.0005). Within reference streams, mean age was significantly higher in upstream
sections (by 0.7 years) compared to downstream sections (P=0.0157). There was also a
significant difference between the below sections of barrier and reference streams with
the barrier below section consisting of older white suckers (P=0.0002).

As with rainbow trout, a regression of white sucker fish length on fin ray radius
was used to back-calculate previous lengths at age (Figure 18). The regressions of
previous length at age on incremental growth was analyzed for each stream pair to
examine differences in grth between stream types (Figure 19, Figure 20). Based on
the AN COVA, stream type showed a significant interaction with previous length at age
(P=0.0046) and growth was not found to be significantly different between barrier and
reference streams (P=0.7707).

For all streams, catch curves were created to detect differences in white sucker
mortality. White suckers were fully selected by the backpack electroshocker at age two,
therefore, age zero and age one fish were excluded (Figure 21). Since fish older than age
one were not caught in the East Whitefish River, I excluded this pair from this analysis.
An AN COVA performed on the slopes of the regressions showed a significant difference

in instantaneous mortality rate between the barrier and reference stream (Pst W .

=0.0128).

age

63

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64

160
140
120

0 East Branch AuGres
y = -0.1556x + 96.676

I West Branch Rifle
y = -0.2461x + 107.98

 

401

Incremental Growth (mm)
on
O

E. AuGres

 

 

 

 

 

W. Rifle \ \ o
0 j l I I I l
0 100 200 300 400 500 600
Previous Length at Age (mm)
o Miners
140 y = -0.1503x + 96.431
A 120 I Harlow
E 100 y = -0.437x + 81.898
3;?
9 80
(9
g 60
E 40 - . Mlners
0
E
20 ~
0 7 I I I I l
0 100 200 300 400 500 600

Previous Length at Age (mm)

Figure 19. Growth of white sucker for East Branch AuGres/ West Branch
Rifle pair (top) and Miners/Harlow pair (bottom).

65

   
 
 

 

 

 

 

 

140 0 West Whitefish
y = -0.3802x + 84.636
E 120 I East Whitefish
g 100
i
9 80
(D
.79 60
5 W. Whitefish
E 40 -
a:
E
_ 20 a
o I I I
0 50 100 150
Previous Length at Age (mm)
0 Middle
12° y = -0.3966x + 80.374
A 100 I Poplar
E y = -0.2444x + 77.698
IE; 80
B
2 60
.g a
E 40 -
5 Poplar
‘ 20 ~ N
Middle
0 I I I I I I
0 50 100 150 200 250 300
Previous Length at Age (mm)

Figure 20. Growth of white sucker for West Whitefish/East Whitefish pair
(top) and Middle/Poplar pair (bottom).

66

 

 

 

 

   

 

 

 

35 j 0 East Branch AuGres
g 3 o d y = -o.4813x + 2.9577
g 25 . .\ I West Branch Rifle
.5 3 2.0 . 0 ‘ y = -0.6675x + 4.2009
a: 3 9
3 8 1.5 ~
g 1.0 ~
g 0.5 .
0.0 . .
0 5 1o 15
Age (years)
b o Miners
8 0.8 1 y = -0.0745x + 0.7338
g 0 6 - ° I Hanow
.2. 8 ' y = -0.6931x + 2.0794
° ’3 0.4 -
3’ s
"’ o
E 0.2 -
8
z 0
0 5 10 15
Age (years)
.. 3-0 1 . Midd'fi) 1542 2 9474
= . x + .
é 2,5 - *8 Middle y
a I Poplar
.2. 8 2-0 ‘ \ y = -0.6931x + 2.0794
0 1'3
773' 81.0 - I'\
§ 0.5 - \ Poplar
2 0.0 . §r . .
0 5 10 15
Age (years)
Figure 21. Natural log transformed catch curves for white suckers

for East Branch AuGresNVest Branch Rifle pair (top). Miners/Harlow
pair (middle), and Middle/Poplar pair (bottom).

67

DISCUSSION

Based on the general habitat characteristics we measured, streams with low-head
barriers showed relatively little habitat alteration when compared to reference streams.
Average width and average maximum depth were found to be significantly higher in
barrier streams, but mean substrate size and mean water temperature was similar between
the two stream types. Based on the River Continuum Concept (V annote et al. 1980), I
anticipated seeing a gradual increase in width, depth, and temperature and a decrease in
substrate size moving in a downstream direction. Both barrier and reference streams
follow this trend of increased width and depth downstream, but sites directly above the
impoundment (Above lsite) are deeper on average compared to those sites in reference
streams (Figure 4). Although we tried to exclude the impoundment from our sampling
protocol, our sites closest to the dam may have been within the impacted zone upstream
of the small reservoir were the stream began to deepen.

According to Ward and Stanford (1983), dams slow the flow of water creating a
reservoir and often act as sediment traps. From this knowledge, sites closest to the dam
(Above 1 sites) would be expected to have a greater portion of fine substrate particles
such as silt and sand and the site directly downstream to have coarser substrate. This was
not evident in our graph of mean substrate size where substrate size is consistent at sites
above and below the barrier (Figure 5). This suggests that these dams are not large
enough to significantly change the substrate composition of the stream. Temperature,
which is often affected by surface release dams such as these, might be expected to

increase directly below the barrier relative to that site in the reference stream (F raley

68

1979). However, we see that average temperature is not appreciably greater directly
below the darn compared to above sites within barrier streams and that the Below 1 sites
in barrier streams are actually cooler on average than the Below 1 sites in reference
streams. This indicates that low-head barrier dams do not retain water long enough to
noticeably increase the temperature of the stream and that the higher temperatures in
reference streams may be due to them being somewhat shallower and narrower, allowing
light to penetrate further down the water column. Beyond the small impoundment above
the dam and the plunge pool just below, barrier dams did not have substantial impacts on
the physical habitat in the study streams.

For community composition between stream positions, species richness was
found to be higher in both upstream and downstream sections of barrier streams relative
to reference streams. This may be due to barrier streams being wider and deeper on
average allowing for more species to be sustained in these streams. Examining temporal
variation of the fish community, little variability in average species richness was evident
between summers for both stream types, indicating that barriers are not impacting the
stability of these streams in terms of number of species caught, although the actual
species present may change from year to year.

Comparing the trends in average width and maximum depth (Figure 4) with those
of average richness and relative abundance (Figure 6, Figure 7), I found that the habitat
characteristics we measured had very little explanatory power on the differences among
stream types. For reference streams, trends in habitat seem to be more closely linked to
trends in average richness and mean abundance. In streams without barriers, average

width, maximum depth, and species richness generally increased in a downstream

69

direction, while catch per area declined from upstream to downstream. With width and
depth increasing in a downstream direction, I anticipated seeing higher numbers of fish
moving downstream. This prediction was not supported in my study for reasons that are
unclear at this time. For streams with low-head barriers, mean width, maximum depth,
and average richness also showed a general increase downstream, but there is a distinct
peak in richness directly below the dam which is not seen for width or depth. Mean catch
for barrier streams also showed a distinct peak below the dams that then declined, but,
unlike species richness, mean catch in above sites declined towards the barriers. The
AN COVA analyses suggested that width and/or depth do explain some variation seen in
species richness and mean abundance, however, the trends between habitat and mean
richness or abundance within barrier streams are not as closely linked as they appear to be
in reference streams, indicating these dams are not influencing the richness and
abundance of the fish community by habitat alteration. A significant number of species,
approximately 2.5 species, were lost upstream due to low-head barrier dams, suggesting
that these barriers are indeed having an impact on species richness in these streams.
When I excluded sea lamprey from the analysis on species lost upstream of the dam, I
found the average loss of species declined slightly to approximately 2.3 species lost
above the barrier. Although barrier streams were significantly different than reference
streams in terms of width and depth, these differences in habitat do not account for the
greater species richness seen in barrier streams, the high number of species found directly
below the dam, nor the greater loss of species within barrier streams.

Characteristics of the barriers were also found to have no explanatory power on

number of species lost above the dam, indicating that the impact of the dam did not

70

increase with the size of the dams in this study. It is important to note, however, that all
of the dams in this study were quite small and that this conclusion does not extend to
dams larger than I examined. From the analyses of habitat and barrier characteristics on
species richness along with the high peak in richness and abundance found directly below
the dam, I conclude that the trends seen in mean species richness and mean relative
abundance within barrier streams can best be explained by the blocking of fish movement
by the darn regardless of its size, resulting in an aggregation of species downstream. An
additive result of the darn may also be an increase in macroinvertebrate drift over the
barrier, thus, increasing the food resource and resulting in continual aggregation of fish
downstream of the dam. Since I did not investigate macroinvertebrate drift over the dam,
I can only speculate as to this being a possible effect of the barrier on the stream
community.

Using reference streams as a guide to expected similarity between upstream and
downstream fish communities, above and below sections of barrier streams are relatively '
similar when compared to the Stbrensen's index for reference streams. If barrier dams
were severely impacting the fish community, the community similarity within barrier
streams would be much lower compared to reference streams. Thus, despite the greater
loss of species above barriers, I concluded that the species composition is quite similar
above and below the barrier. Community size composition was also shown to be similar
between above and below stream sections of barrier and reference streams With no

significant impact of barrier dams on community size. Therefore, at the community level,

71

barriers produce no substantial impact on species composition or size of the fish
community.

As seen from our frequency of occurrence data, low-head barrier dams are
successful in preventing sea lamprey from migrating upstream, however they also appear
to affect movements of some non-target species. Non-jumping species such as yellow
perch, trout-perch, and logperch were negatively impacted by barriers in terms of
frequency of occurrence and mean abundance, indicating that movement of these species
upstream is greatly affected by the dam. Black bullheads were positively affected by the
presence of a low-head barrier dam, which may be due to utilization of the small
impoundment by this species. For native lampreys, such as american brook lamprey, I
suspect the barrier creates a refuge from lampricides due to the fact that only downstream
sections are treated. In this study, low-head barrier dams were shown to affect individual
sensitive species with some species being negatively impacted while others showed a
positive impact in occurrence or abundance.

Since I suspected that low-head dams may block fish fi'om migrating upstream, I
examined the effects of barriers on age and growth of two migrating species: rainbow
trout, a jumping species, and white sucker, a non-jumping species. Because low-head
barrier dams are designed and constructed to allow salmonids to pass, I predicted barriers
would have no significant impact on the age and growth of this species. However, fi'om
my analysis, I found that rainbow trout were significantly younger in barrier streams
particularly downstream of the dam, grew significantly faster, and were less abundant
overall in barrier streams, but showed no differences in instantaneous mortality rate

(Table 12). One possible explanation for faster grth in barrier streams may be due to

72

 

Table 12. Comparisons between barrier and reference streams for age,
growth, mortality, and abundance of rainbow trout (top) and white

suckers (bottom).

 

 

 

 

Rainbow trout BARRIER REFERENCE
MEAN Younger Below Younger Above
AGE Younger Overall Older Overall
GROWTH Faster Slower
MORTALITY No Difference No Difference
MEAN

ABUNDANCE Less Abundant More Abundant
White sucker BARRIER REFERENCE
MEAN Younger Above Younger Below
AGE Older Overall Younger Overall
GROWTH No Difference No Difference
MORTALITY Lower Higher
MEAN

ABUNDANCE More Abundant Less Abundant

 

73

 

density dependent factors. With rainbow trout less abundant in barrier streams, the prey-
to-predator ratio is higher, allowing individual rainbow trout to have access to a higher
number of macroinvertebrates. TFM treatments increases drift of macroinvertebrates
severely (Derrnott and Spence 1984; Kolton et al. 1986). Thus, the stream section above
the dam, where TFM is not used, may act as a refuge creating relatively large populations
of macroinvertebrates. This may also explain the slightly older population of rainbow
trout above the dams where older rainbow trout are traversing the barrier to utilize the
abundant prey resource upstream. A related explanation of faster rainbow trout grth
could be higher drift of macroinvertebrates over the dam 60111 the populations upstream
increasing the prey resource for trout in this area allowing rainbow trout to attain smolt
size (size at time of migration to the Great Lakes) at an earlier age shifting the population
age structure to a younger mean age.

Another explanation for faster rainbow trout growth might be higher productivity
in streams with dams. Streams with low-head barriers were chosen for darn construction
based on the fact that these streams had high production of sea lamprey. Since larval sea
lamprey are filter-feeders, they thrive better in streams with higher course (CPOM) and
fine particulate organic matter (F POM) (Moore and Mallatt 1980). This nutrient source is
also a major diet component of many aquatic macroinvertebrates (Merritt and Cummins
1996), thus, streams with more CPOM and FPOM, should produce higher biomass of
macroinvertebrates, a major prey source for rainbow trout (Scott and Crossman 1973)
allowing rainbow trout to grow faster in streams with barrier dams. Because I did not

measure productivity or macroinvertebrate composition/numbers, I can only speculate as

74

 

to the mechanisms affecting the growth and age structure of rainbow trout in barrier
streams.

Since adult white suckers also feed on aquatic insects (Trembly and Magnan
1991; Hayes et. al. 1992), I would expect a higher macroinvertebrate fauna to also
produce an increase in grth of white sucker. However, this was not observed in the
data (Table 12). One plausible reason to explain a lack of difference in growth between
stream types assuming barrier streams are more productive may be due to intraspecific
and interspecific competition. White suckers are more abundant in barrier streams
possibly increasing competition among the population and, due to white suckers also
feeding on invertebrates, they might be out competed by other species such as the
territorial rainbow trout for similar food resources (Scott and Crossman 1973). Trembly
and Magnan (1991) found evidence of competition of food resources between white
sucker and brook trout, but, in their study, white sucker out competed brook trout shifting
the diet of brook trout from zoobethos to zooplankton. Because trout in the stream feed
in the water column whereas juvenile and adult white sucker feed on the bottom
(including macroinvertebrates), the possibility of higher macroinvertebrate drift across
the barrier (which was speculated to increase rainbow trout growth in barrier streams)
would not benefit the white sucker. Therefore, the availability of macroinvertebrates to
this species may be similar between stream types regardless of a possibly higher prey
source in barrier streams.

Like macroinvertebrates and native lamprey, white suckers are also adversely

affected by TFM treatments especially during times of stress (Dahl and McDonald 1980),

75

 

thus, barrier dams may act as a refuge upstream lowering mortality in barrier streams
overall.

According to the literature (Dahl and McDonald 1980; Hunn and Youngs 1980),
white suckers are unable to move across the barrier and therefore unable to migrate
upstream to spawn. From the information in the literature, I anticipated a perched
population of white suckers upstream which were younger on average than the population
downstream due to the inability for spawning adults to traverse the barrier moving
upstream but able to traverse moving downstream during feeding migration. From my
analysis, I found white suckers to be older overall in barrier streams but significantly
younger above dams, suggesting that low-head dams may be impacting the age structure
of the upstream population by acting as a source of mortality for above sections. Another
possible explanation rrright be that older larger white suckers utilize the impoundment,
acting as a population source, but went undetected in the study because the reservoir was
not sampled. According to Errnan (1973), white suckers increased in abundance and were
smaller upstream of the reservoir after dam construction, with larger fish being caught in
the impoundment. He attributed this to utilization of the reservoir by larger white suckers
while smaller suckers remained in the stream. As such, I conclude that although some
non-jumping species may not be able to maintain their populations above barriers (i.e.
yellow perch or trout-perch), white suckers are either able to traverse the barrier when
water levels are high during the spring or to maintain their population despite an

impairment to movement (i.e. use of reservoir for protection or food by lager fish).

76

 

 

CONCLUSIONS

Although barrier streams were found to be significantly wider and deeper than
reference streams, there was relatively little effect of the barrier on the general habitat
measurements we examined. An impact on number of species seen above the barrier dam
was evident, but width and maximum depth could not explain the trend of high species
richness below the dam nor the greater loss of species upstream of the barrier. Therefore,
I conclude that the major mechanism of impact on species richness is the blocking of fish
movement upstream, although at the community level, low-head barriers had a relatively
small influence on species composition or community size composition between
upstream and downstream sections.

In this study, low-head barriers were found to be effective in blocking sea
lamprey, reducing the amount of stream needing treatment by lampricides, but had
relatively little effect on stream habitat and fish communities. Although I found an
average loss of 2.5 species upstream, a portion of that loss can be attributed to the loss of
sea lamprey above the darn. Other fish species that were completely blocked by the
barriers were yellow perch and trout-perch. Although yellow perch is a game species in
the Great Lakes, this fish is primarily a lentic species that may use calm rivers during
certain life stages such as spawning or feeding (Scott and Crossman 1973). The trout-
perch, both a lentic and lotic species, mature at age one with most dying after spawning
only once (Kinney 1950; Scott and Crossman 1973). Although barriers affect the
distribution of trout-perch within the stream, the residence time of this species in streams

is low such that barriers may not have a severe impact on the population age structure or

77

growth. Therefore, the average loss of 2.5 species due to the dams can be considered to be
a biologically minor impact on the stream community.

In some cases, barrier dams appeared to have a positive effect possibly through
creation of habitat immediately upstream or downstream of the dam or creation of a
refuge from chemical treatments (particularly for native lampreys). Further study is
needed to determine the specific mechanisms of impact on potentially sensitive species.

Rainbow trout age and growth showed to be impacted within barrier streams by a
mechanism(s) that is unclear and which may become apparent with further study of the
productivity and macroinvertebrate fauna of barrier streams. Contrary to the literature,
white suckers did not appear to be negatively affected by the presence of a barrier in
terms of overall abundance, growth, or mortality. As stated previously, this may be due
to white suckers traversing the barrier during times of breach or the ability of white
suckers to sustain a population despite blockage to movement.

In conclusion, our results show low-head barrier dams have relatively little impact
on the fish community and are a viable alternative to other sea lamprey control methods.
By building these low-head barrier dams the amount of TFM applied to the stream
ecosystem can be reduced benefiting fish species sensitive to chemical treatments (i.e.
native larnpreys and white suckers) as well as their prey sources (i.e. macroinvertebrates).
As such, the low-head barrier dam control program should be continued as a
supplemental method to reduce the use of lampricides in Great Lakes tributaries while

maintaining sea lamprey abundance at target levels.

78

APPENDICES

79

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LITERATURE CITED

85

LITERATURE CITED

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88

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