THE ’c'FFECTS OE FISH
PREDATiON UPON BENTHlC FAUNA

Thesis fior the Degree 0! M, S.

MtCHLGAN STATE UNIVERSITY

Ronald WayneRybicki
19.62

 

   

\mL

LIBRA 1‘; '1'

Michigan State
University

THE EFFECTS-OF FISH PREDATICN UPON BENTHIC FAUNA

RONALD WAYNE RYBICKI

A mESIS

Submitted to the College of Agriculture of Michigan State
University of Agriculture and Applied Science in
partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Fisheries and Wildlife
1962

Approved by QM M

1"

an!

U9 ‘

a,
-,.--v

*-
CA4:

“

pe-

ABSTRACT

Evaluation of the exclosure method as a means of estimating the
effects of fish predation upon its macro-invertebrate food supply was
undertaken at the lake City Experimental Station during the summer of
1959. Also included in the study were the effects of fish predation.
fish growth, seasonal trend of the invertebrate population, and
periphyton.

Large and small exclosures were used to detect whether exclosure
size influenced significantly the standing.crops of benthic fauna with-
in the exclosures. No significant heterogeneity was found between the
mean weights of benthic fauna sampled from the large and small exp
closures.

The seasonal trend observed in the invertebrate populations was
thought to be the result of insect emergpnce.

Invertebrate samples were drawn from both inside and outside of i
the exclosures in a fish predation-free pond to detect whether or not
the exclosures were attracting the benthic organisms. No attraction

for the bottom organisms by the exclosures was found.

Differences between the weights of bottom fauna sampled inside
and outside of the exclosures in the ponds which contained fish preda-
tors were considered to be the quantity of fish-food consumed. Pre-
dation intensity was found to be directly related to fish growth.

Fish growth also appeared to be inversely related to stocking
ratios. Fish populations at a density of 200 pounds per acre exp
hibited less growth than those at a density of 1A0 pounds per acre.

No correlation was fbund between the standing crops of periphyton
and benthic fauna. There was no time-lag factor by which a change in
periphyton could be correlated with a change at the trophic level of the

benthic fauna.

ACKNOWLEDGEMENTS

The author wishes to acknowledge with sincere appreciation-and
gratitude the guidance and thoughtfulness of Dr. Robert C. Ball, under
whose direction this research program was carried out. Special thanks
are also due to Dr. Don Hayne for experimental designj Dr. Phillip J.
Clerk for his help on the statistical analysis; Mr. Richard Bennett

for his field assistance; and to the staff at the Lake City Experiment

Station. The study was made possible through a graduate research

assistantship of the Michigan Agricultural Experiment Station.

TABLE OF 00ng

Page
IN‘EODUCTION.00000.00.00.000...00......O00......OOOCOOOOOOOOOOOOO 7

DESCRIPTION or STUDY AREA........................................ 8
METHODS.......................................................... 10
Pond Divisions and Exclosures..........;.................... 10
Benthic Fauna Sampling Procedure............................ 11
Periphyton Sampling......................................... 12

Pond Preparation............................................ 1h

Fish Handling and Stocking.................................. 15

Need Control................................................ 16
Statistical Methods......................................... 16
RESULTS.......................................................... 17
Large-Small Exclosure Comparisons........................... 17
Exclosure~0utside Area Comparisons.......................... 17
Effect of Fish Predation.................................... 18

Fish Growth................................................. 18

. . Seasonal Trend.............................................. 18
Periphyton...................L.............................. 19
DISCUSSION....................................................... zq
Benthic Fauna..t............................................ 20
Large-Small Enclosure Comparisons........................... 21
Exclosure-Outside Area Comparisons.......................... 23
Effects of Fish Predation................................... 23

Fish Growth................................................. 26
Seasonal Trend.............................................. 30

PeriphytonOOOOOOOOOOOOOOOOOOOOOOCOO...OOOOOOOOOOOOOOOOCOOOOOO 37

SUMYOOCOOOOOOOOOOOIOOOOOOOOOO0......OOOOOOOOOOOOOOOOOOOOOOOOO. ha

LITWTURE CITED...00....OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO-O... L5

Table Number
1

Appendix

LIST or mug

Average depth and surface area of each pond
section.

Size classes and pounds per acre of fish stocked
in each pond section.

The order in which numbered plexiglass plates
were placed and collected.

Comparisons of the mean weights of bottom fauna
per unit area from the large and small exclosures
to those from the outside area.

Tests for weekly differences between the mean
weights of benthic fauna per unit area from.ex-
closures and outside areas.

Pounds of fish-food consumed per acre per week,
confidence limdts for the consumption values,.
and total (pantity of fish-food consumed over
the 11 week period. ‘

Summary of fish stocking, harvesting and mean
growth data. Growth is in ounces per fish,
stocking and harvesting figures are in pounds
per acre.

Tests for fluctuations in benthic fauna per unit
area between weeks. Large and small exclosure
data are combined.

Phytopigment absorbencies and the conversions
from absorbencies to milligrams of periphyton
organic matter per square decimater per day.

Tabular summary of benthic fauna weights.

Numbers and mean- lengths of benthic fauna
families for section AI.

10

16

19

2h

25

27

29

37

h8-53

5&971
72-75

Figure Number
I

II

III-VIII

LIST OF FIGURES

Page
Diagram of the Lake City experimental ponds. 9
The relationship between mean fish growth and 28

stocking ratios.

Weekly fluctuations of weights of benthic fauna 31-36
smoothed by two. From exclosures and outside
areas, sections AI, AII, BI, BII, CI and CII.

Standing crops of periphyton in milligrams per hO-LZ
square decimeter per colonization period for all
sections. The mean standing crop for each three

~18 day cycle is shown by the histogram for each

pond section. ‘

W

Since fish and fish products are an integral part of the nation's
economy and are expected to become even more so it will be necessary
to meet the present and future demands for increased production of fish.
One of the basic requirements to fulfill this demand is the understand-
ing of the relationships between a fish population and its source of
food. One such relationship is the effects of predation by a fish
population upon its macro-invertebrate foody supply. .

One method of estimating the effects of fish predation upon the
invertebrate fauna is by the use of exclosures. An exclosure creates
an area which is not subject to fish predation. Ideally, the differ-
ences between the quantities of benthic fauna inside the exclosures
and the area exposed to fish predation represent the quantities of
fish food consumed.

Such a method was used by Welch (1958) to estimate the effects of
fish predation upon the benthic food organisms. His work raised two
vital questions: (1) do exclosures tend to attract the benthic fauna?
and, (2) does exclosure size influence the number of bottom organisms
within the structure? Clearly, should any such effects occur, the exp
closure method of estimating fish predation would have to be modified
to be useful. .

The purpose of this study was to determine the validity of’the
exclosure method in estimating fish predation. Included in this in-
vestigation was a study of the effects of fish predation, fish growth,
seasonal trend of benthic fauna and periphyton. The periphyton data

were used to explore the relationship between standing creps of

periphyton and benthic fauna.

The study began on June 22, 1959, and was completed on September
9, 1959.

DESCRIPTION OF THE STUDY AREA

The Fisheries and Wildlife Department of Michigan State University
maintains and utilizes for research purposes six ponds at the Lake City
Experiment Station. The station is located two miles south and one-
half mile east of Lake City, Missaukee County, Michigan.

The six.ponds were constructed during l9hh immediately down-
stream from an already existing 6.6 acre reservoir (Chapoton, 1955).
The general layout of the reservoir and ponds is shown in Figure I.

The reservoir had been formed by damning the upper basin of
Mosquito Creek, a tributary of the Clam River. The lower and deeper
end has a maximum.depth of about five feet, and the bottom material is
composed primarily of pulpy peat. The shallow, upper end is choked
with ghagg, Potamogeton,p§gph§g_and Typha. There remains in the
shallow parts of the reservoir large numbers of tree trunks and stumps.
In addition to supplying water for the ponds, the reservoir is used
extensively for irrigation purposes.

Ponds A and B are connected to the reservoir by short, shallow
channels. Ponds C and D receive their water supply through under-
ground pipes, which are connected to a holding pond. The holding pond
in turn is linked to the reservoir by a culvert.

Inflow and outflow of the four ponds is regulated by adjustable
board gates. The remaining two ponds, when used, must have water

pumped in from the reservoir.

 

Figure I. Diagram of the Lake City Experimental ponds.

 

 

24212.2 .Eo mxfi
mozoa ..<azm2.mm¢xm

/

25322

 

 

.3380:

 

 

10

The inlet structures of ponds A and B are of poured concrete,
while the inlets of pond C and D are constructed boxplike of heavy,
treated timbers. All outlet structures are of poured concrete.

Ponds A, B and C were used in this study (Figure I). Each was
divided into two sections, creating a total of six sections. The
area and average depth for each section are given below.

Table 1. Average depth and surface area of each pond section.

Section Averagg Depth Area Sacres)
AI 2.0 feet 0.2665
All 1.5 feet 0.1068
BI 2.0 feet 0.2L30
BII 2.0 feet 0.2166
CI 2.7 feet 0.0750
CII 3.0 feet 0.0750

The pond bottoms are muck, except along the lower contours which

have been flushed down to sand and gravel by drainage currents.
‘ Ponds A and B contained primarily Chara and Potamogeton .
ctinatus, while pond C exhibited only slight submergent plant growth.

£32535, Typha, Sagittaria and Scigpus were found around the perimeter
of all ponds. Only pond B produced significant filamentous algal
growth during the investigation.

Aquatic Odonata, Tendipedidae, Heleidae and Heptageneidae were
the dominant benthic organisms in all pond sections.

METHODS AND PROCEDURES

Pond Divisions and Exclosureg,

Each of the three ponds was divided into two sections by a hard-

ll

ware cloth fence (two meshes to the inch and 36 inches deep), for a
total of six sections. The sections were designated as Al, AII, BI,
BII, CI and CII (Figure I).

In the fish predation study of 1958, only one size of exclosure
was used -- a hardware cloth structure of l.5'x.l.5‘ x 1.5' dimensions.
Two sizes of exclosures were used in this investigation -- a circular
type six feet in diameter and 36 inches deep, and the smaller structures
used in 1958. The small exclosures were also equipped with a remova-
ble lid, since they were often completely submerged. All exclosures
were constructed of quarter-inch hardware cloth.

Each of the six pond sections contained one large exclosure and
two small exclosures. A grid pattern of exclosure placement was used.
The small exclosures were placed approximately eight feet from the
center of the large exclosure. Caution was used when placing the ex.
closures to insure that there were no openings along the bottom edge
through which fish might enter. .

The exclosures in pond A were moved once each week; pond B exp
closures were moved once every two weeks; section CI exclosure move-
ment corresponded to the exclosure movement of pond B, and CII exp
closures were relocated weekly to coincide with that of pond A.
Benthic Fauna Sampling Procedure,

All pond sections were sampled on three successive days of each
week over an lleweek period with an Ekman dredge (one-fourth square
foot capacity). The dredge samples were taken only after the
exclosures had been in place fer one week. Four bottom samples (one

square foot) were removed from each of the large exclosures, two

bottom samples from each of the small exclosures, and four\dredge
samples from the outside area, i.e., the area exposed to fish pre-
dation. Stakes were used to mark the sampled areas in those exp
closures which were moved once every two weeks. A total of 88 bottom
samples was taken from.each pond section over the llrweek period.

The dredge samples were processed as follows: a series of four
bottom samples was taken, the silt removed by washing through a sieve
at the pond site, then taken to the laboratory and picked. The bottom
fauna was separated from the debris by the use of a saturated sugar
solution (2.5 pounds of sugar per gallon of water). The organisms
from each sample were placed directly in a labeled vial containing
70 per cent alcohol. After all pond sections had been sampled and the
samples sorted, the organisms collected were soaked in tap water fer
30 minutes to restore body fluids lost while in the preservative, then
placed in a clinical centrifuge and the excess water removed at 1800
r.p.m. for three minutes. The organisms were weighed immediately on
a torsion balance with no regard to taxonomic classification and re-
preserved. Only for section AI were the benthic fauna samples
identified to family, and the numbers of individuals and the mean
lengths recorded. These data are recorded in Appendix C, page 72.
Eggiphxton Sampling, .

Periphyton in this study is defined as all flora which has
permanently attached itself to or settled upon the artificial substrate.

Artificial substrates of plexiglass seven millimeters thick with
an exposed surface area of 150 square centimeters were used to sample

the periphyton community. A rack to support the plexiglass plates

13

was constructed from a steel fence post with a wooden cross member
adjustable for vertical movement. The cross member was designed to
accommodate a maximum of eight plates at any one time. The plates
were held secure by ouarter-inch stove bolts with wingnuts. The sub-
strates were placed about eight inches below the water's surface.

The plates were exposed to periphyton colonization for intervals
of 3, 6, 9, 12, 15 and 18 days. The plate rotation plan used was that
first designed by Dr. Don Hayne in connection with periphyton growth
studies, and is as follows:

A. On the first day plates 1, 2, 3, A, 5, and 6 were placed on

the racks.

B. On the fourth day plates 1 and 2 were removed and 7, 8, 9,

and 10 were added.

C. On the 13th day plates 9, 10, 3 and A were removed and 11 and

12 were added.

D. On the 19th day plates 5, 6, 7, 8, 11 and 12 were removed.
The cycle was repeated four times in each pond section during the
course of the problem.

The plates were collected at the proper intervals and placed in
plastic freezer bags for convenience of transport from the ponds to
the laboratory. Periphyton removal from the upper side of the plates
was accomplished by scrapping with a glass microscope slide and
rinsing the slide, plate and freezer bag with 95 per cent ethanol into
a 250 milliliter beaker. Complete extraction of the chlorophyll was
assured by soaking the material for a period of at least 2L hours in
total darkness (Stokes, per. comm.). Ninety-five per cent ethanol was

used as the chlorOphyll solvent in preference to acetone because the

latter is also a plexiglass solvent.

After chlorophyll extraction was complete, the mixture was
filtered throughwglass wool to remove plant cells and other organic
matter. The filtrate was then increased to a volume of 50 milliliters,
'using 95 per cent ethanol. Absorbency was read in a Klett-Summerson
colorimeter to determine the phytopigment density. Readings were made
using a red filter (660 mm) to remove the interference. of'non-plant
pigments. Investigation by Grezenda and Brehmer (1960) showed that
plant pigment absorbency values hold true up to an optical density of
2.0, but after that begin to decrease with increasing concentrations
and do not follow the Lambert-Beer Law. None of the readings in this
investigation approached 2.0 and therefore needed no correction.

The conversion from absorbency values to milligrams of organic
matter per square decimeter per day was accomplished by utilizing the
regression equation expressing the relationship between phytopigment
absorbency and total organic matter (Grezenda and Brehmer op. cit.):

Y = 1.72 . 82.37X, where Y is the predicted weight and x is the

absorbency corrected for the Lambert-Beer Law.
Pong2§rgparation.

Each inlet gate was equipped with a screen consisting of quarter-
inch hardware cloth and a fine, copper screen facing. These screens
prevented the ingress of small fish from.the reservoir when the ponds
were being filled or the water level controlled.

Hardware cloth dividers were positioned prior to filling the
‘ponds. Care was exercised in anchoring the bottom edge so that there

would be no invasion by fish from one section to another.

15

Fish Handling and StockingI
The fish in this investigation were dependent upon the benthic

fauna as a source of food. The sunfish were made available through
the courtesy of the Michigan Conservation Department.

Beginning on June 22, the ponds were drained slowly to induce
fish congregation at the deep end of the ponds. Slow drainage also
decreased the possibility of fish being trapped in the weeds. The
fish were removed and placed in the holding pond where they were
measured, a fin clipped, and returned to the pond which was being
filled. Fin clipping was done in the event of accidental fish in—
filtration from one section to the other and for identification at the
end of the problem.

Essentially the same procedure was used at the end of the in-
vestigation. To expedite fish removal from the upper sections, a
modified fish trap was inserted in the wire divider at the deepest
point; short hardware cloth wings guided the fish into the trap while
the pond was being drained. As the fish were captured they were again
placed in the holding pond, measured and weighed.

The fish populations of section AI were the bluegill (Lepomis
macrochirus), pumpkinseed (Lepomis gibbosus) and the black bullhead
(Ictalurus malag). Sections All, BI and BII contained only bluegills
and pumpkinseeds. Bullheads were readily available and so were used
to compensate for the shortage of sunfish in section AI. Pond C was
designated as the control pond and, therefore, was not stocked. The
ratio of bluegills to pumpkinseeds was approximately four to one.

The sunfiSh were sorted into two length classes prior to plant-

16

ing -- less than five inches and five inches and greater. The stock-
ing data are given in Table 2.

Table 2. Size classes and pounds per acre of fish stocked in each
pond section.

Section -Pounds PoundsZAcre
less than 5 inches
5 inches plus
AI Sunfish . h 10 . 78
' Bullheads 9
All Sunfish A 16 ' 200
BI Sunfish - 3A ILO
BII Sunfish 15 20 17L
CI

Not stocked
CII

'All dead fish observed within three days after planting were replaced
by living substitutes of comparable size.
“bed Control.

No herbicides were used to control any type of plant growth since
it was believed that such material might be toxic to fish and benthic
organisms.

Because of the prevailing winds, the mats of filamentous algae
tended to collect at one end of the ponds and were easily removed with
a hardware cloth seine. Emergent plants were cut periodically with a
hand scythe to prevent their becoming a nuisance.

Statistical Methods.

Analysis of variance - Model I with four observations per cell

-- was used to detect significant differences between the mean weights

of benthic fauna sampled from (1) large and small exclosures, (2) large

1?

exclosures and outside areas and (3) small exclosures and outside
areas.~ Heights of benthic fauna are on a per unit area basis.
BEfiUDTS
Wm
Large and small exclosures were used to detect whether exclosure
size influenced significantly the standing crepe of benthic fauna
within the exclosures.
‘No significant heterogeneity was found between the mean benthic
fauna weights per unit area sampled from the large and small exclosures.
If exclosures tend to attract the benthic fauna. then the ex-
closures which were moved once every two weeks should have signifi-
cantly greater mean standing craps per unit area than those which were
moved once each week. Since pond 0 had no fish predators. CI ex-
closures were mcved once each week and CII exclosures were rotated once
every two weeks. Nb significant difference (at the five per cent level)
occurred between the mean weights of benthic fauna per unit area
sampled from.the exclosures moved weekly and bi-weekly.
ggcloggrg-Outside 5:33 Compggigogga

The mean standing crops per unit area from the large and small ex-
closures were significantly greater than the mean standing crap per unit
area from.the outside area of section 31. The data from section 011 in-
dicated that the mean weights of benthic fauna per unit area sampled
from.the large exclosure were significantly greater than those from the
outside area (Table t)-

!he mean weights of benthic fauna samples from the large ex-

18

closure, section CI, and the small exclosures, sections BI and BII,
differed significantly from those of the respective outside area
during one or more weeks (interaction effects, Table 5).

Effects of Fish Predation,

In Table 6 are presented the predation values in pounds of benthic
fauna consumed per acre per week, and.the confidence limits for those
values. The relationship between food consumption and growth was
tested by the Rank Order method of correlation and found to be signi-
ficant at the five per cent level.

The ratios of pounds of fish-food consumed to the mean weight in-
crease of the surviving fish are as follows: AI--L:1; BI-7:1;
BII--3:1. Section AII showed a weight loss of 0.2 ounces per fish and
is not included in the preceding.

Fish Growth.

The growth, stocking and recovery data are summarized in Table
7. Section BI fish exhibited the greatest gain in weight per in-
dividual (0.7 ounces), while section All fish lost 0.1.me per in—
dividual. .

The bullheads in section AI also showed a slight decrease in
weight (0.01 ounces per fish) over the season. With the exception of
B1, the total fish biomass decreased from.June to September.

Seasonal Trend,

The combined measurements of the large and small exclosures were
used to detect differences in the mean weights of bottom fauna samples
between weeks, since exclosures reduced fish predation to a minimum.

The data from sections BI, BII, CI and CII indicated significant

l9

differences between the mean standing crops of benthic organisms on a
weekly basis (Table 8 and Figures III - VIII).
Periphytgn,

The plexiglass plates were exposed to periphyton colonization
from three to 18 days. The order in which the numbered plexiglass
plates were placed for colonization is given below.

'Table 3. The order in which numbered plexiglass plates were placed
' and collected. c .

Day Plates Plate Nos. Plate Nos. Day Plates No. Days

Placed Placed Collected Collected §§p2g2g_

1st 1,2,3,4,5,6 - - ' -
Lth 7,8,9,10 1,2 ‘ 1th 3
13th 11,12 3,1 13th 12

9,10 . 9

5.6 19th 18

7,8 15

11,12 6

The three through 18 days of periphyton colonization collectively
have been designated as a cycle. Standing crop values for periphyton
have been plotted fer each pond section (Figures IX - XI). The cycles
for sections I and II of all ponds are represented by the broken and
solid lines, respectively. The mean standing crop for each cycle is
depicted by the histogram. The conversions-from.phytopigment ab—
sorbencies to milligrams of organic matter per square decimeter per
day are given in Appendix A.

The mean periphyton growth was greatest between June 30 and July
15, followed by a low point from July 19 to August 3.

In general, the three or six day colonization period of each cycle

showed the largest standing crop, while the remaining colonization

20

periods (nine through 18 days) exhibited a drOp and/or leveling
pattern.

No correlation was found between the mean standing crap of
periphyton and benthic fauna, nor was any time-lag factor apparent
before the possible effect of an increase or decrease in periphyton
was evident at the trophic level of the benthic fauna.

DISCUSSION
Benthic Fauna,

To determine the predator-prey relationship between a fish pOpu-
lation and its invertebrate food supply, it is necessary to study the
macroéinvertebrate fauna quantitatively. Ricker (l9h6) states, "All
macroscopic organisms can serve as food for fishes, so any quanti-
tative study of the occurrence of such organisms is of potential value
in estimating the ability of that body of water to support fish.”

Eshenour (1953) and Ball (19h8) concluded that bluegills turned
to plant food as the supply of animal food diminished; Howell, Swingle
and Smith (19L1) also came to the conclusion that animal food was
”preferred”. In this study it is believed that animal food was
always abundant.

Wilkins (1952), Ball and Hayne (1952) and Eshenour (op. cit.)
used various methods to estimate the effects of fish predation upon
the benthic food supply. The exclosure technique has the advantage
of portable size, thus readily creating numerous, predation-free areas
with a minimum of effort expended.

It is probable that predation upon the benthic population by

other invertebrates also occurred. It is assumed, however, that pre-

21

dation by invertebrates was of a comparable magnitude both inside and

outside of the exclosures.

Large-Small Exclosure Compgrisons.

 

Since the differences between the mean weights per unit area of
benthic fauna from the large and small exclosures were not significant,
it is concluded that exclosure size did not influence appreciably the
presence of benthic fauna. The totals of the standing crops of bottom
organisms per unit area for the 11-week period from the small ex-
closures were slightly larger than those from.the large exclosure in
five out of the six pond sections (Appendix B, pages it, 60, 63, 66,
69), even though the mean weights per unit area of benthic fauna
between exclosures did not differ significantly.

This seemingly contradictory statement may perhaps be explained
by the aquatic life cycle of the odonata. Odonata naiads complete
their aquatic life cycle on some emergent object (Usinger, 1956).
Molted odonata skins were observed clinging to both the inside and
outside of the emergent portion of the large exclosures, suggesting
that the exclosure had served as a suitable emergent object.

The small exclosures were constructed from quarter-inch hardware
cloth and had removable lids, and the structures were submerged a con-
siderable portion of the time. As a result, the larger species of
odonata naiads may have experienced some difficulty in escaping
through the small mesh to complete their life cycle. As a consequence,
these particular naiads may have fallen victim to the dredge, while
those in the large, Open exclosures were able to escape. Such a

slight influence by the small exclosures would be mechanical in nature

22

and could be avoided either by using large exclosures only, or by in-
creasing the mesh size of the small exclosure to one-half inch.

It is conjectured that, where fish predators were present, weekly
exclosure movement might not allow the benthic fauna population to be-
come established prior to sampling. For this reason pond A exclosures
were moved weekly and pbnd B exclosures were relocated once every two
weeks (bi-weekly) . 4'

A predation—free, two-week period may have allowed an increase
in the weight of the benthic fauna within the exclosures. If this is
true, then the first samples of the bi-weekly sampling series should
be consistently smaller than the second samples of the series. The
first samples should show less weight because the exclosure had been
moved to an area previously subjected to fish predation, while the
papulation in the second sample of the bi-weekly series had sufficient
. time for additional weight increase - due either to an increase in
population numbers because of exclosure attraction, or to growth.

Fifty per cent of the time the first samples taken were at least
“as large, or larger than, the second samples taken from the same exp
closure. It is concluded that benthic populations sampled from one
and two week predation-free periods are not appreciably different.

There is no evidence to suggest that the exclosures tend to
attract the benthic fauna.“ If such were the case, then the mean
weight of bottom organisms per unit area from the combined large and
small exclosures in section CII (moved once each week) should have
been significantly less than that from section CI (exclosures were
[moved once every two weeks), particularly since pond C had no fish

predators. The mean weights of benthic fauna from the CII exclosures

23

were not significantly less at the five per cent level than the mean
weight of benthic fauna from.section CI exclosures (which were similar
to the CII exclosures in size).

Exclosure-Outside Area Comparisons.

Both mean weights per unit.area of the bottom fauna samples from
the large and small exclosures were significantly greater than the
mean weights per unit area of the benthic population sampled from the
outside area in section BI (Table A). This section showed the only
significant fish predation effects, as well as the greatest fish
growth and the lowest mortality rate (10.9 per cent). Sections AI,
AII and BII exhibited fish predation effects of a relatively small
magnitude and the fish grew less.

Pond C had no fish predators and, hypothetically, should have
shown no predation effects. Therefore, it is surprising that the
mean standing crap of bottom organisms per unit area from within the
CII small exclosures should be significantly greater than that fer the
outside area (Table 4). The weights of the invertebrate samples
drawn from the small exclosures during the weeks of August 12th and
26th were unusually large (Appendix B, page 71) and may account for
the discrepancy.

The mean weights of invertebrates per unit area from the ex,
closures were significantly greater than those from the outside area
during one or more weeks in sections BI and BII (Table 5). This is
thought to be due to predation upon the benthic fauna by the fish.

Effects of Fish Predation,

' Since a direct relationship was found between fish growth and

2h

 

 

 

Table A. Comparisons of the mean weights of bottom fauna per unit
area from the large and small exclosures to those from the
outside areas.

Small Exclosure-Outside Area
Pond Variance df ,
Section s2 s2 E ' I F F
E I .
.95
AI 0.0121 0.02h0 1 10 0.51 h.96
AII 0.00h0 0.02h8 1' 10 ' 0.16 6.96
BI 0.2292 0.0LAS' l 10 5.15* h.96
BII 0.199h 0.0752 1 10 2.65 b.96
CI 0.009L 0.0165 1 10 0.59 b.96
CII 0.0811 0.0112 ‘ l 10 7.27* L.96
Large Enclosure-Outside Area
Pond Variance df
Section 5% a} E I F F
. .95
AI 0.0089 0.0300 1 10 0.30 h.96
\
AII 0.000A 0.0202 1 10 0.02 h.96
BI 0.1359 0.0129 1 10 10.56* b.96
BII. 0.0279 0.0168 1 10 1.66 h.96
CI 0.0309 0.0557 1 10 0.56 L.96
CII 0.0136 0.0310 1 10 2.28 5.96

*Significant at the five per cent level.
E --'Excloeure variance
I - Interaction variance

25

 

 

Table 5. Tests for weekly differences between the mean weights of
benthic fauna per unit area from exclosures and outside
areas.

Small ExclasuresJOutside Areas-week;
Pond Variance df
Section a? 33/1" . I w/in F F.”
AI 0.0240 0.0606 10 66 0.h0 1.98
AII ‘ 0.02h8 0.0147 10 66 1.69 1.98
BI 0.0Lh5 0.01L8 10 66 3.00* 1.98
BII 0.0752 0.0308 .10 66 2.Lk* 1.98
CI 0.0165 0.0229 10 66 0.72 1.98
CII 0.0112 0.0185 10 66 0.60 1.98
Largg Exclosure-Outside Areas-weeks
Pond Variance df
Section a? aw/in I w/in F F.95
AI 0.0300 0.0190 _10 66 1.58 1.98
All 0.0201 '0.0188 10 66 1.08 1.98
BI 0.0129 0.0132 10 66 0.97 1.98
BII 0.0168 0.0066 10 66 2.62* 1.98
CI 0.0557 0.0249 10 66 2.23* 1.98
CII 0.0310 0.0160 10 66 1.93 1.98

*Significant at the five per cent level.
I -— Interaction variance
w/in - Within groups variance

26

predation values, this phase of the study is in agreement with Moore

(1961) and Gerking (1955) who found that food consumption is directly
related to fish growth. The pounds of fish-food consumed per acre per
week, and the confidence limits for these values are given in Table 6.

The conversion ratio of pounds of fish-food consumed to the
weight increase of the surviving fish was 6:1, 7:1, and 3:1 for
sections AI, BI and BII, respectively. This is quite variable when
compared to the 6:1 conversion ratio observed by Hayne and Ball (1956)
in bluegill populations. Helch (op. cit.) noted a 6:1 ratio for blue-
gills in the same ponds used in the present study. Of the available
fish-food, the fish utilized 15.6%, 6.3%, 52.5% and 36.0% in sections
AI, AII, BI and BII, respectively.

Fish Growth.

Figure II shows the relationship between growth of fish and
stocking ratios. It is interesting to note that section AII had the
heaviest fish stocking ratio (200 pounds per acre) and showed the
least predation effects, as well as a weight loss of 0.2 ounces per
fish. The fish population in AI was stocked at 78 pounds per acre
and gained 0.2 ounces per surviving bluegill. The fish in BI ex-
hibited an increase of 0.7 ounces per fish (stocked at 160 pounds per
acre) and also showed the greatest predatory effects. A stocking
ratio of 176 pounds of fish per acre in section BII resulted in an in-
crease of only 0.2 ounces per fish. The relatively poor growth for
the high density populations suggests that the optimum stocking rats
had been exceeded. Smith and Swingle (1960) observed that bluegills
at high population densities consumed less food and, consequently,

showed less growth than fish stocked at lower densities.

27

 

 

 

0.0mH 0450.0m .bOHm.om mmHm.MH m4m4.MH ®No¢.om memo.ma HHm
o.Hmn . mmoe.om memo.em aowa.am Hamm.mm ~mma.om moma.om Hm
5.5H «mos.o emem.m eman.e mmmm.o anoq.e swam.m HH<
H.mm eeeH.HH omam.o meea.oa mom~.m omea.m mmme.s H4
goon: uoaoq goon: scion
oceancoo
neesoa H6669 o as o as on u we on . gs conuoom
gasses conseneeoo “we ecoa

ocoooaaon Adv nunwponnsm
.nodas> coapasdmcoo on» you

.soum oowupso one on use .nossmoHoXo Hanan Amy and owned

.voaneo x003 Ha one so>o usadmcoo eoouusnau mo hpfiussso Hepop use
nadsaa oocoeamcoo .xoo: use once you eossmcoo ooouunmfim no needom .0 cases

 

Figure II. The relationship between mean fish growth and stocking
ratios.

Stocking - pounds per acre

28

230‘

220.

l90-

I70:

ISO:

ISO-

HO:

90-1

 

7G - r

 

-02 on 02 04 05 05

Mean weight increase in ounces

29

 

 

 

 

 

o.mo and 45a b¢.d om.H HHm
H.0m . 00H 04H oo.~ . mo.a Hm
4.H> oma com 0H.H Hm.H HH<
No.m >0.m noeozaasn
m.o> mu ms
. _ $4 34 33mg?
1. - _ . H4
86166.5 an: 63th $383. tots: messes“
eofiaoem
mo hso>ooom m as A.onHV pzwaos Heuoa as A.sov games: use: ecom

.eaoa use season :H and schema“ euo>asn use mcaxooao Havoc
.muwm you wooedo ca aw nazoao .sueo sazoam zoos one wcaauo>uen .mcaxoopm seam mo hameadm .b canoe

30

The bullheads in'section AI also exhibited a slight decrease in
weight -- 0.1 ounces per fish. Nikolsky and Kukuskin (1963) dis-
covered that the food consumption of speckled bullheads was greater
in unmixed than in mixed populations. Bluegills comprised 76 per cent
of the fish population in section AI. Since no marks were given to
identify fish greater and less than five inches in the mdxed size
populations, the growth rate for each size group is not knowrn
Seasonal Trend, '

Ball and Hayne (1952) found a definite seasonal trend in the
concentration of benthic fauna populations in lakes. They noted a
volume reduction (due to the emergence of adults) in the spring
following the ice break-up with the volume reaching the lowest point ‘
in August. In the present investigation the maximum standing crop
generally occurred during late June and again the first two weeks of
August (Figures III - VIII). The June low points probably represent
a decreased population because of spring emergence of adults, while
the July increase implies additional population growth.

The exclosures were used to detect weekly fluctuations because
fish predation effects were thus reduced to a minimum. Significant
weekly (Table 8) fluctuations are probably due to emergence, and
perhaps influenced by fish predation in sections BI and BII. With
the absence of fish predators in Pond C, the weekly fluctuations are
thought to be caused by emergence.

In Appendix.c are presented the numbers and mean sizes of benthic
fauna sampled from the small exclosures and outside 69;. of section

AI.

Figure III. Weekly fluctuations of weights of benthic fauna
smoothed by two. From.exclosures and outside
areas, section AI, 1959.

”2i

|.O4i

.96:

.881

.80:

.72-

.6 4‘

.56-

.48-

Grams per square foot

.40:

.32-

.24:

.I6-

\

_ Large exclosure

--- Small exclosure

-e- Outside area /
O

‘s

, 2'

\o“‘

l
l.

“e

' I

’1
e’.’

31

 

 

:08
29m

June

on

Isth 20th
July

2'7". 3rd {om

Sampling date

August

fi—

I7th 24th inst 7th

September

 

Figure IV. Weekly fluctuations of weights of benthic fauna
smoothed by two. From exclosures and outside
areas, section AII, 1959.

Grams per square foot

LIZ”

.se-
. as-
.so
.72‘
.e4«
.56-
.4s~
.40-
.32.

. 24q

.08:

.00-

32

a . '
l \ .
I ‘\ I \ — Large exclosure
" y e '
'0 \‘ \ —-- ,Small exclosure
' ' “ .
" I -.- Outside area
0' ' \
\ e
' I . \
. \‘
' O
"I I \“ \ ,
I
. I \ \ I
' ° \ . I
\\ '
‘ ’l e
_./ ‘V” \‘

 

 

29th 6th l3fl'l 201'h 27th 3rd IOth l7th ‘24th 38? 7th

June

July August September

Sampling date

 

Figure V. Weekly fluctuations of weights of benthic fauna smoothed
by two. From exclosures and outside areas, section B1,
1959. '

° .80:

Grams per square foot

33

l.60'
|.50-
L40-
L304
|.20-
I. lO-l
LOO:

.90:

.70-
.60-

.50+ ’

.40 .f'\

.30 /° \ .
.2. .\//

.IO-

 

 

.OC ' V .I U U V I I I I
30m 7th l4‘ih 2lst 28th 4th llfl'l l81h 25th IS? 8th

June July August September

Sampling date

Figure VI.

weekly fluctuations of weights of benthic fauna smoothed
by two. From exclosures and outside areas, section BII,

1959.

_ V ,. ..__- fi—--—— .

Grams per square foot

LIZ-l

.96-l

.884

.80‘

.724

.64-

.56:

.48:

.40:

.32-

.24-

.l6-

 

31.

_ Large exclosure

--- Small exclosu re

\ -e. Outside area

 

.08
30th

June

I

7th I4ih 2|Si 28th 4th llih |8th 25m IS? 81h
' July August September

Sampling date

Figure VII. Weekly fluctuations of weights of benthic fauna
smoothed by two. From exclosures and outside areas,
section CI, 1959.

Grams per square foot

' .24.

LIZ-

|.04-

.96:

.88'

.80-

.72 a

.64-

.56-

.40-

.32 '

'8'-
O

 

— Large exclosure
--- Small exclosure

-e- Outside area

   

 

35

 

lst

"I'th

ls'tn 22'na 25th 5'». lath Is'tn 26th

July

August

Sampling date

'—

2nd 9th
September

Figure VIII. weekly fluctuations of weights of benthic fauna
smoothed by two. From exclosures and outside areas,
section CII, 1959.

Grams per square foot

|.O4«
eel
.ss«

.80:

.64«
.56t
.48-
.40-

.321

.08-

 

.04

36

— Large exclosure ’ ‘~ “I

a..- Small exclosure I

-.- Outside area I I

 

 

lst

8th

I5th 22nd 29th 5m 12m I9th 26m énd 7.6
July August September.

Sampling date

37

Table 8. Tests for fluctuations in benthic fauna per unit area
between weeks. Large and small exclosure data are combined.

Pond Variance df

 

Section s3 Sw/in w w/in F F.95
AI 0.06L7 0.0630 10 66 0.71 1.98
AII 0.0116 0.0135 10 66 0.86 1.98
BI 0.0685 0.0260 10 66 2.25* 1.98
BII 0.0861 0.0326 10 66 2.6h* 1.98
CI 0.0696 0.0298 10 66 2.33* 1.98
CII 0.0515 0.0093 10 66 5.53” 1.98

*Significant at the five per cent level.
df - Degrees of freedom
w --- weeks
w/in -- within groups variance
Periphyton.

The standing crops of periphyton were measured to determine their
relationship to the standing crops of benthic fauna. Castenholz (1960)
states, "Certainly the attached algae (periphyton) should not be
ignored in studies of primary production, particularly in smaller
bodies of water where their contribution may be great."

Periphyton includes sedimentation of phytoplankton upon the
plexiglass plates as well as the attached algae. In this study the
periphyton community appeared to have been composed chiefly of
filimentous algae, although Castenholz (op. cit.) found that almost
all of the ash from fresh water attached material was composed of in-

tact diatom frustules.

The patterns of periphyton growth compared favorably with those

38

observed by Castenholz. welch (1952) states, "In the permanent ponds
.... the plankton may be expected to show annual maxima (i.e. spring

and autumn)...." The periphyton standing crop at the beginning of the
project is probably the declining tail of the spring maximum, While the
last increase is the beginning of the fall maximum (Figures IX--XI).

The minimum standing crops of periphyton occurred during the cycles of
July 19 - August 3, and August 6 — 21. This corresponds to the summer
minimum suggested by Welsh (op. cit.). Since the ponds were so shallow,
lack of nutrients due to a thermocline could not have caused a mid-
summer lull in the standing crop of periphyton. Other explanations

for this phenomenon may be temperature, light, or interspecific
competition between flora. ,

The decrease in rate of production after the three or six day
colonization period is perhaps caused by initial rapid colonization
of the plates and then a forming of the population at a slower and
more uniform rate.

The "pulses” which occur in each cycle may represent periphyton
turnover. Birge and Juday (1922) suggest a one to two week plankton
turnover; Juday (1960), in his energy budget for lake Hendota, uses
two weeks as the year-round average, although Hutchinson (1961) sus-
pects that the turnover is at a faster rate.

No correlation was found between standing crops of periphyton
and benthic fauna. In this connection Riley (1960) found no corre-
lation between plankton standing crops and gross production in
Linsley Pond. Rawson (1953) is of the Opinion that the relatively
small range between plankton standing crops in oligotrOphic and

eutrophic lakes give little encouragement to hope that the measurement

39

of standing crops will be of much use as an index of productivity.
Lindeman (1960) states, "mile the relationships of nannoplankton to
rotifers, and those of net plankton to Chaobourus have been noted as
suggesting predator-prey dynamics, browsers and predators varied
tremendously and independently.I He further states that an abundance
of green plants does not necessarily indicate an abundance of animals

as consumers.

Figure IX.

Standing craps of periphyton in milligrams per square
decimeter per colonization period are represented by
the broken and solid lines for sections AI and AII,
respectively. The mean standing crop for each three-
18 day cycle is shown by the solid and open histograms
for sections AI and AII, respectively.

5:32.23 2 3398 {so

        

   

       

          

 

 

 

 

 
 

 

 

 

6.36m ems... .N.o=<- 0.2.2 no.2- 61.2. 922.- on 2.2.
m.m.N.mmm_m. m. N. o o m_m_m. N. m m m_m_ m. N. m m m
n n L p n n p a L n n n b n n p n p n 0.0
.o.N
0‘
be
.06
a
6.0
1"}.
6.0.
«530.3338 9.655 "U . .o.N.
NEo\_e>..oE.\ao..o 2.32m I
m... ozoa . . 6.:
Ee\e.o>o\ae._o 9.655 6.0.
N . I
use \.e>._eE.\ no.0 2.32m Inll
H< ozoo on.

0.0N

ieieullaep 9.10an 10d suiaibgmw

Figure 1.

Standing crops of periphyton in milligrams per square
decimeter per colonization period are represented by the
broken and solid lines for sections BI and BII, re-
spectively. The mean standing crop for each three-18

day cycle is shown by the solid and open histograms for
sections BI and BII, respectively.

.1.
l.~

  

man—ow ¢N63<
0. m. N. m 0 M—m.

m.

.N .u...< ®.a=<

N.

3.35.3.3 o. eoaonxo £60

a m m_0.

-

m.

 

 

  

    

 

~Ee\ e_o>o\ no.5 9556
use .oZoE.\ no.0 useczm

...l..m 020m

«Eu \ o .98 \ no.8 2655
use \ 522.5 no.8 2.22m

H0 029.

N. m

mas... o. 22“. .

0

L

     

92.... - on 22.

m_m. m. N.

n

 

m

0

m

 

'ieieuigoep OJDflbS Jed swmbmm

Figure XI. Standing crOps of periphyton in milligrams per square
decimeter per colonization period are represented by
the broken and solid lines for sections CI and CII,
respectively. The mean standing crop for each three-
18 day cycle is shown by the solid and open histograms
for sections CI and CII, respectively.

5:32.23 2 3398 goo

a mfiomémdi _N.a:< - m .o:< m .22 - 2 3:1 m. 32., n on 2.57
m._.Im_N_ome.m._ m. «r. m o m_m_ m. m._ o o m_m_ m. m. o m m

       

 

   

 

   

 

 

 

 

so
10..
[ON
:0.”
'.
.Oé
§
. .
a A m
..
6.0
..
. . ow
«53203220 2656 n. .
«Eo\_o>._££\ao._o 9.655 I — . - 6.0
No ozon. — .
a . .od
. a
Eu\o_o>o\aoao ac. co ca .06.
u .u a I -
uso\.o>..2c_\ao._o 3655 II... a. 0.:
Ho ozoa .1
’ . tocm.
III! .
a an.

 

Jejemgoap unnbs 10d swmbgmw

2.

A3

SUMMARY

Large and small exclosures were used to determine whether or not
exclosure size influenced significantly the standing crops of
benthic fauna within the exclosures. The large exclosures did
not show significantly larger standing crops per unit area of

benthic fauna than did the small exclosures.

Movement of the exclosures once each week and once every two
weeks was used to determine if a longer time would result in a
greater population buildup of benthic fauna,.thus suggesting
the presence or absence of exclosure attraction for the bottom
organisms. No exclosure attraction for.the benthic fauna was

found.

The mean weights of bottom organisms per unit area from the ex-
closures were significantly greater than the comparable mean
weight of benthic fauna from the outside area of section BI.

This is attributed to fish predation on the benthic invertebrates

in the outside area.

The mean weight of invertebrates per unit area from the exp
closures were significantly greater than those from the outside
areas during one or more weeks in sections BI and BII. This is

thought to be the result of fish predation upon the benthic fauna.

The consumption of fish-food was found to be directly related to

fish growth.

LL

Fish population densities were found to be inversely related to

fish growth.

weekly fluctuations of the invertebrate pepulations within the

exclosures were perhaps due to insect emergence.

No correlation was found between the standing crops of periphyton
and benthic fauna, nor was any time-lag factor apparent before
the possible effect of an increase or decrease in periphyton was

evident at the traphic level of benthic fauna.

LS

LITERATURE CITED

Ball, Robert C.
l9h8 Relationship between available fish-food, feeding habits of
fish and total fish production in a Michigan lake. Tech.
Bull. 206, Michigan State Univ. Ag. EXp. Sta.’
Ball, Robert C. and Don W. Hayne

1952 Effects of the removal of the fish population on the fish-
food organisms of a lake. Ecology, 33(1): hl-LB.

Birge, E.A. and C. Juday
1922 The inland lakes of Wisconsin. The plankton, its quantity
and composition. Bull. Wisconsin Geol. Nat. Hist. Surv.
No. 64: l-222.
Castenholz, Richard W.
1960 Seasonal changes in the attached algae of freshwater and
saline lakes in the lower Grand Coulee, Washington. Limnol.
and Oceanog., 5(1): 1-28.
Chapoton, Robert B.
1955 Growth characteristics of the northern redbelly dace
Chrosomus‘ggg (Cope) in experimental ponds in northern
Michigan. Unpub. Master’s Thesis,'Michigan State Univ.
Library.
Eshenour, Robert William

1953 The effects of fish predation on the bottom fauna of a small
pond. Unpub. Master's Thesis, Michigan State Univ. Library.

Gerking, Shelby D.
1955 Influence of rate of feeding on body composition and pro-
tein metabolism of bluegill sunfish. Physiol. 2001., 28:
267.282 0
Gresenda, Alfred R. and Morris L. Brehmer

1960 A quantitative method for the collection and measurement of
stream periphyton. Limnol. and oceanog. 5(2): 190-197.

A6

Hayne, Don W. and Robert C. Ball

1956 Benthic productivity as influenced by fish predation.
Limnol. and Oceanog., 1(3): 162-175.

Howell, Henry H., H. s. Swingle and B.V. Smith

19Ll Bass and bream food in Alabama waters. Alabama Cons.,l
1(h): 3.

Hutchinson, G. I.
19Ll Limnological studies in Connecticut. VII. A critical
examination of the supposed relationship between phyto-
plankton periodicity and chemical changes in water.
Ecology, 25(1): 3-26.
Juday, C.

19L0 The annual energy budget of an inland lake. Ecology,
21(9): ABS'hSOI

Lindeman, Raymond L.

' 1941 Seasonal food cycle dynamics in a senescent lake. Am.
Midl. Nat., 26: 636-673.

Moore, Walter G.

19L1 Studies on the feeding habits of fishes. Ecology, 22(1):
91-96 0

Nikolsky, and Kukuskin

19h} 0n the influence of population density upon food consumption
of fishes. Zool. Zhurnal, 22(2): 73-76.

Pennak, Robert W.

1953 Fresh water vertebrates of the United States. Ronald Press,
'01. , 769 Pp.

Rawson, D.S.

1953 The standing crop of net plankton in lakes. J. Fish. Res.
Ed. Canada, 10(5): 22L—237.

Ricker, William E.

19h6 Production and utilization of fish populations. Ecol.
Monog., 16: 373-391.

L7

Riley, G. A.

1940 Limnological studies in Connecticut. II. The plankton in
Linsley Pond. Ecol. Monog., 10: 279-306.

saith, E. v. and H. s. Swingle

19A0 Winter and summer growth of bluegills in fertilized ponds.
Trans. All. Fiat]. 5°C., 70: 335-338.

Usinger, Robert L.

1956 Aquatic insects of California. Univ. of California Press
Berkley and Los Angeles, 508 pp.

‘Walker, Helen M. and Joseph Lev
1953 Statistical Inference. Henry Holt and Company, N.Y., 510 pp.
Welch, Gene B.
I 1959 The predator—prey relationships between a fish population
and-its macro-invertebrate food supply. Unpub. Master's
Thesis, Michigan State Univ. Library.
Welch, Paul S.

1952 Limnology. HcGrawaHill, N.Y., 538 pp.

APPENDIX A

Phytopigment absorbencies and the conversions from ab-

L8

sorbency to milligrams of organic matter per square deci-
meter per day.

 

Pond Days of Exposure Mean anic
Section gggycle to Colonization A_‘Absorbency Matter/dmélpa
AI June 30- 3 0.350 9.0365
July 15 6 0.680 9.3352

9 0.798 7.1123

12 0.514 3.38h8

‘15 0.1.1.8 2.31.51.

18 0.585 2.5811;

July 10- 0.320 8.2128
Aug. 3 6 0.331 b.257h
9 0.1.66 6.0738

12 0.620 L.1121.

15 0.L78 2.5101

18 0.1.90 2.0337

Aug. 6- 3 0.135 3-1333
Aug. 21 6 0.327 h.1613
9 0.1.07 3.5338

12 0.Lh6 2.9180

15 0.670 3.5616

18 0.603 2.6638

' Aug. 21.. 0.326 8.3775
Sept. 9 6 0.229 2.8571
9 0.561» b.9707

12 3 0.81.8 . 5.6771:

15 0.621. 3.3119

18 0.862 3.81.90

L9

 

Continued.

Pond Days of EXposure ‘ Mean Hg. of Dr anic
Section Cyf}3_- t0 Colonization Absorbency Hatter/0m /Day

AII June 30— 3 0.680 18.0972

July 15 6 1.080 1h.5390

9 0.1.15 3.6070

12 0.611 h.0506

15 0.h2h 2.2136

18 0.L29 1.8675

July 19- 3 0.386 10.0219

Aug. 3 6 0.168 2.0196

9 0.21.0 3.0051.

12 0.331. 2.11.92

15 0oh22 1.0Lh0

18 0.365 1.57117

Aug. 6- 3 0.101 2.1997

Aug. 21 6 0.3A7 A.L77O

9 0.L7L b.1L70

12 0.691 3.2269

15 0.638 3.3885

18 0.603 2.6638

Aug. 2L— 3 0.250 6.2908

Sept. 9 6 0.231 2.8845

9 0.635 5.6205

12 0.576 3.8100

15 0.769 b.1081

18 0.581 2.5631

50

 

Continued.

Pond Days of Ecposure Mean Mg. of Or anic
Section Cycle to Colonization Absorbency Matter/dmg/Day

BI June 30- 3 0.375 9.7229

July 15 6 0.900 10.7110

9 0.h20 3.6528

12 0.866 5.7873

15 1.119 6.0301

18 0.758 3.3731

July 19- 3 0.079 1.5621.

Aug. 3 6 0.155 1.81.12

9 0.1115 1.1389

12 0.197 1.2089

15 0.130 0.8737

18 0.219 0.9066

Aug. 6- 3 0.091 1.9252

Aug. 21 6 0.295 3.7631

9 0.193 1.5752

12 0.280 1.7786

15 0.358 1.8512

18 0.500 2.1925

Aug. 21- 3 0.058 1.0191

Sept. 9 6 0.180 2.18151.

. 9 0.11.1. 1.1268

12 0.176 1.06157

15 0.3811 1.99150

18 0.375 1.6201.

51

 

Continued.

Pond Days of Emposure Mean Hg. of 0r anic
Section Cycle _:_ to Colonization Absorbency Matter/ng/qu

BII June 30- 3 0.155 3.6820

«”15 6 QMZ mam

9 A 0.380 3.2867

12 0.L70 3.0828

15 0.L2h 2.2136

18 0.630 2.7873

July 19- 3 0.087 1.8153

Aug. 3 0.210 2.5961

9 0.13h 1.0352

12 0.277 1.7580

15 0.260 1.3130

18 0.210 1.1969

Aug. 6- 3 0.126 3.1333

Aug. 21 6 0.320 1.1061.

A 9 0.225 1.8681

12 0.295 1.8815

15 0.318 1.6315

18 0.6A5 2.8560

Aug. 21.. 3 0.100 2.1723

Sept. 9 6 0.1.1.5 5.8221.

9 0.329 2.8199

12 0.536 3.5358

15 0.592 3.1362

18 0.750 . 3.3365

52

 

Continued.

Pond Days of Exposure Mean Hg. 0f 0r anic
Section Cycle to Colonization Absorbency Hatter/duE/Day

CI June 30- 3 0.190 b.6h3h

July 15 6 1.068 13.0101

9 1.369 12.3382

12 1.AAO 9.7h10

15 0.922 Lo9h83

18 0.1.67 2.0.11.

July 19— 3 0.153 3.6275

Aug. 3 6 0.285 3.6259

9 0.110 0.8163

12 0.159 0.9680

15 0.192 0.9396

18 0.296 1.2589

Aug. 6- 3 0.111 2.L7h3

Aug. 21 6 0.370 6.7928

9 0-12h 0.9037

12 0.152 0.9000

15 0.LA1 2.3070

18 0.650 1.9179

Aug. 2L- 3 0.106 2.3370

Sept. 9 6 0.187 2.2805

9 ° 0.335 2.8708

12 0.531 3.5015

15 1.L20 7.6830

18 1.365 6.1508

53

 

Continued.

Pond Days of Exposure Mean Hg. of Dr anic
Section Cycle t0 Colonization ‘Absorbency Hatter/0m /Day

CII June 30- 3 0.180 6.3688

July 15 6 0.690 8.8330

9 0.885 6.1886

12 1.161 7.8259

15 0.683 3.6359

18 0.850 3.79h1

July 19— 3 0.06h 1.1838

Aug. 3 6 0.289 3.6808

9 0.122 0.925h

12 0.231 1.6A22

15 0.199 0.9781

18 0.135 0.5222

Aug. 6- 3 0.119 2.69h0

Aug. 21 6 0.252 3.1728

9 0.180 1.h517

12 0.208 1.28LA

15 0.3h0 1.7523

18 0.399 1.7303

Aug. Zh— 3 0.111 2.h7h3

Sept. 9 6 0.3h0 L.3809

9 0.Ah6 3.8907

12 0.723 b.8191

15 0.775 A.1A11

18 1.389 6.2606

APPENDIX B

55

Weights of bottom organisms collected from the large exclosure and
comparable outside areas, Section AI. The data were converted to
grams per square foot per week.

Week Grans/eane foot Grams/square foot Combined
Large exclosure ' Outside area Samples
6-29 0.71.10 0.392 1.136
7- 6 0.102 0.31.0 0.1.112
7-13 0.595 0.122 0.717
7-20 0.213 0.381. ' 0. 597
7-27 1.363 0.398 1.761
8- 3 0.21.0 1.132 1.372
8-10 0.227 0. 537 0. 8116
8-17 0.713 0.1079 1.192
8-26 0.1.96 0.19? 0.693
8-31 0.668 0.625 1.293
9- 7 9.13.9.3. 9.1315. .2121}.
Total 5 .759 l. . 371 10. 630

60

Weights of bottom organisms collected from large and small exclosures,
Section BI. The data were converted to grams per sqzare foot per week.

Week cram/aqua. foot Grams/square foot Combined
Large exclosure Shall exclosure Sanples
6-30 0.193 0.096 0.289
7- 7 0.1.07 0.769 1.176
7-1:. 1.095 0.311. 1.1.09
7-21 0.89:. 0.752 1.61.6
7—28 0.871 1.1.37 2.308
8- I. 0.632 2.173 2.805
8.11 0.11.5 0.760 0.905
8-18 1.090 ' 0.180 1.270
8-25 0.561 0.1.08 0.968
9- 1 0.1.1.2 0.1.72 0.911.
9- 8 ‘ 2.252 9.55.3 .9412:
Total 6.586 7.619 11.305

.61

Weiglts of bottom organisms collected from the large exclosure and
comparable outside areas, Section 81. The data were converted to grams

per square foot per week.

Week Grams/square foot Grams/square foot Combined
Large exclosure ‘ Outside area Samples
6-30 0.193 0.208 0.L01
7'- 7 0.1.07 0.275 0.682
7-16 1.095 0.387 1.1.82
7-21 0.896 0.335 1.229
7-28 0.871 0.196 1.367
8- A 0.632 0.338 0.970
8-11 0.1h5 0.209 0.356
8-18 1.090 0.125 1.215
8-25 0.561 0.233 0.79h
9- 1 0.LL2 0.3h7 0.739
9- 8 285.6 91171 9.1.11
Total 6.586 3.128 9.71h

62

‘Weights of bottoa.organisms collected from saall exclosures and compa-
rable outside areas, Section BI. The data were converted to grams
per square foot per week.

Week Grams/square foot Grams/square foot Combined
Small exclosure ~ Out side area Samples
6-30 0.096 0.208 ' 0.30L
7- 7 0.769 0.275 1.06A
7-IL 0.31L 0.387 0.701
7-21 0.752 0.335 1.087
7-28 1.A37 0.A96 1.933
8- A 2.137 0.338 2.511
' 8-11 0.760 0.209 0.969
8-18 0.180 0.125 0.305
8-25 0.1.08 0.233 0.61.1
9- 1 0.L72 0.317 0.819
9- 8 2.252 2.125 .0203
Total 7.619 3.128 10.7h7

63

Weights of bottom organisms collected from large and small exclosures,
Section BII. The data were converted to game per sqaare foot per week.

week '. 5 Grus/smare foot (hams/swan foot Combined
Large exclosure Snll exclosure Samples
'6-30 0.057 0.11.2 0.199
7- 7 0.8h3 0.995 1.738
7-1L 0.18A 0.570 '0.75h
7-21 0.597 ' 0.733 1.330
7-28 0.565 0.h23 0.938
8- A 0.322 0.532 0.856
8-11 0.369 0.227 0.575
8-18 0.1.18 0.395 0.813
8-25 0.233 0.292 0.525
9- 1 0.878 0.317 1.195
9- 8 2.152 9.369 111.19
Total I. .603 7 .227 11 .830

61.

Weigats of bottom organisms collected from the large exclosure and
comparable outside areas, Section BII. The data were converted to
grams per smare foot per week.

Week Gram s/sane foot A Grams/ square foot Combined
Large exclosure ' Outside area Samples
6-30 0.057 0.160 0.217
7- 7 0.81.3 0.119 0.962
7-11. 0.181. 0.1.19 0.603
7-21 0.597 0.256 ‘ 0.853
7-28 0.565 0.352 0.917
8- I. 0.322 0.211 0.533
8.11 0.31.9 0.571 0.919
8-18 0.1.18 0.106 0.522
8-25 0.233 0.1.81 0.711.
9- 1 0.878 0.112 0.990
9- 8 9.152 9.251 9.1.12
Total 6.603 3.038 7.61.1

65

Heights of bottom organisms collected from ansll enhance and comps-
rsble outside areas, SectiOn BII. The data were converted to grams
per scysre foot per week.

Week Grams/square foot Grams/square foot Combined
3311 exclosure Outside area Samples
6-30 0.1.1.2 0.160 0.302
7- 7 0.995 0.119 1.111.
7-1h 0.570 0.h19 0.989
7-21 0.733 0.256 0.939
7-28 0.1.23 0.352 0.775
8. I. 0.532 0.21.1 0.7103
' 8-11 0.22? 0.571 0.798
8-18 0.395 0.101. 0.199
8-25 0.292 0.1.81 0.773
9- 1 0.317 0.112 0.1029
9' 8 9.1.9.69 9.1322 443.13.
Total ' . 7.227 3.038 10.265

Heights of bottom organisms collected from large end well exclosures,
Section CI. The data were converted to yams per sqasre foot per week.

7...;

'iieek Grams/scalars toot Grams/square foot Combined
Large exclosure fill exclosure Smples
7- 1 0.189 0.113 0.302
7- 8 0.1.01 0.21.0 0.61.1
7-15 0.235 0.557 0.792
7-22 0.536 0.390 0.962
7.29 0.333 0.599 0.932
8- 5 0.271 0.771 1.01.2
8-12 1.176 0.1.96 1.672
8-19 0.800 0.998 1.798
8-26 0. 520 0.322 0.81.2
9- 2 2.161 0.872 3.033
9- 9 9.1.11 9.252 .1491
7.036 6.311

13 .31.?

67

Heights of bottom organisms collected from the large exclosure and
comparable outside areas, Section CI. The data were converted to
grams per square foot per week.

Heek Grams/square foot Grams/agave foot Combined
Large exclosure . Outside area Sailplee
7- 1 0.189 0.057 0.266
7- 8 0.L01 0.671 1.072
7-15 0.235 0.207 0.1.1.2
7-22 0.536 0.186 0.722
7-29 0.333 0.596 0.929
8- 5 0.271 0.51L 0.785
8-12 1.176 1.131 2.307
8-19 0.800 0.736 1.536
8-26 0.520 0.169 0.689
9- 2 2.161 0.175 2.336
9' 9 9AM 94.953 .1132;
Total 7.036 5.388 12.1.2.

68

Weights of bottom organisms collected from small exclosures and compa-
rable outside areas, Section CI. The data were converted to grams per
sqaare foot per week.

Week Grams/square foot . Grams/square foot Combined
Smll exclosure ' Outside area Samples
7- 1 0.113 0.057 0.170
7- 8 0.21.0 0.671 0.911
7-15 0.557 0.207 0.7610
7-22 ' 0.390 0.186 0. 576
7-29 0.599 0.596 1.195
8- 5 0.771 0.511. 1.285
8-12 0.1.96 1.131 ‘ 1.627
8-19 0.998 0.731. 1.732
8-26 0.322 0.169 0.1091
9- 2 0.872 0.175 1.01.7
9‘ 9 9.1.22 9.13% .1139;
Total 6.311 5.388 11.699

69

Heights of bottom organisms collected from.1arge and small exclosures,
Section CII. The data were converted to grams per square {bot per week.

Week Grams/square foot Grams/square foot Combined
Large exclosure Small exclosure - Samples
7- 1 0.160 0.175 0.335
7- 8 0.509 0.090 0.599
7-15 0.215 0.181. 0.399
7-22 0.369 0.310 0.679
7.29 0.1.1.1. 0.538 0.982
8- 5 0.36h 0.389 0.753
8-12 0.386 1.111 1.h97
8-19 0.796 0.902 1.696
8-26 0.357 1.m0 1.1.27
9- 2 0.hhh 0.839 1.283
9' 9 1:329 1:321 .3152}
Total 5.262 6.811 12.103

7O

Heights of bottom organisms collected from the large exclosure and
comparable outside areas, Section CII. The data were converted to
grams per square foot per week.

Week Grams/square foot Grams/square foot Combined
Large exclosure Outside area Samples
7- 1 0.160 0.056 0.216
7- 8 0.509 0.168 0.677
7-15 '0.215 0.333 , 0.5h3
7422 0.369 0.138 0.507
7-29 0.LLL 0.657 1.101
8-‘5 0.36h 0.091 0.L55
8-12 0.386 0.h32 0.818
8-19 0.79L 0.296 1.090
8.26 0.357 0.1.67 0.821.
9- 2 0.111 O.h52 0.896
94 9 1.2.2.9 1.921 1.2.91
Total 5.260 h.168 9.130

71

Heights of bottom organisms collected from small exclosures and compa-
rable outside areas, Section CII. The data were converted to grams

per square foot per week.

Week Grams/square toot Grams/square foot Combined
Snell exclosure Outside area Samples
-7- 1 0.175 0.076 0.231
7- 8 0.090 0.168 0.258
7-15 0. 181. 0.333 0. 517
7-22 0.310 0.138 0.1.1.8
7.29 0.538 . 0.657 1.195
8- 5 0.389 0.091 0.1.80
8-12 1.111 0.1.32 1.51.3
8—19 0.” 0.296 1.198
8.26 1.070 0.1.67 1.537
9- 2 0.839 0.1.52 ' 1.291
9- 9 1.231 1.972 2.3.11
Total 6.311 11.168 11.009

APPENDIX C

Numbers and mean lengths of benthic fauna according to family

for each collection date from the small exclosure, Section AI.

72

H.N
0H

0.H

0.HH

0.0a

m.a
ma

amum

m.a

0.ma

0.5

4.1

ma

n.~
ma

amtm

«.0
0H

0.0

m.N
mm

haum

m.4

o.a

«.0

mm

0.mH

0.4

H.m

>.N
on

0.0

Calm

mum

mfidd

N.H

“.0

8365

.1-5
mm

swab

0.H
n.m

rm
0.“

1...

_0.m

0.5

0.m
04H

b.m

omlb

m.m
ab

0.m

mans

o.~
00H

H.m

01>

1.~
ma
H.m

0.HH

auto

214 20-1 20-1 21-1 20-1 29-1 214 20-3 24

gas

853::

«causeway»:

..ew.a.=

oaeangaoc

omvaowaso

osvwcomuwmcooo

oecduonomno

 

.an nausea

.uoaanas<

oevacmooo<

HflHx<h

73

N.4
N0

0.5
H .
0.NH

515

4.4
Om
0.5

0.HH

am1m

6...
0m

n.m

4N10

. a.

up}

 

6...

55

6.1

«.5

5H10

6...
am

0.5

OHIm

.emeaoadaada :4 newcua sees sameneumom 11 Ass

.nauwcsmuo no nomad: nauseoumem 11 2s

«.4 4.4 5.4 m.4 _ m.m 0.m A
00 00 .omH 5H 4m Ho 2 emvacemaocea
o.“ 6.2. «.4 m.“ 2m . .. 4
m m 4 m 4 1 z omvwdwsaocadq
0.5 m.5 0.4 0.4 0.4 4.0 A
mm o 5 H NH m z omvwasaaonaq

n.m 26-. o~-h na-a. 6-2 .~.6

mydd HAHde

Numbers and mean lengths of benthic fauna according to family

fer each collection date from the outside areas, Section AI.

74

4.5

ON
0 O H
01 F1 F1
H H

C) e\u\ «3&1 51C) r4<3
O
.3 ex
14

e
‘O

515

0.mH

0.H

n.04

«.mm

Hmum

Fa"

 

I"

 

7.9.1115
I ' .l O.“

1 1 - N
5.: 5.: 6.. mg.

4 4 AH mm

1 u o; o;

1 1 N , N
.2. “.2 .2. 5.4

s 3 N N
0.2 6.2 0.5 3.

N m .1 N
1 0:4 oi m.m

1 H H m
o.“ “:1 cs m...

m 6. m a
o.N o.n 6N m.N

m l. on mN

1 o.m 1 5.n

- H - .1
1N.w 54.6. 011m «.6

MB<Q

0.4

0.0

o...
S

m...
3

0.m

5~|5

5.0

0.4

0.0

m.m
H5

m.H

0N15

m.m
0H

nan5

«.5
ma

N.m
m5

015

4.0

.m.N

.N
.2

o...

5N10

2204 £204 £214 £214 :204

3214 2214 :204 :214

oaeflaflnn.caaa

omcwasaaoan

mcwueoeauhz

omeaaaoz

oaeasneou

omcdoaazo

oduacofiaweqooo

 

.mo mwcowo

«81:29.2

oecacnono<

HAHx<m

4.4
m4

515

0N

Amnm

.onevoaAAAAs :4 :amcmA coca nacoeeumom 11 Ass

.nauAsemno no memes: eacononaom 11 2s

.m.m 5.4 5.4 m.4 0.m 5.4 1 m.0 0.0 A

0 no 55 3 3 8n 1 an S 2 836.6389

4N10 5410 OHIm mum 5NI5 0N15 MH15 015 5NI0
0940 MAHx<b

Pm USE LU

--—.

:1121
6'
W 3

 

 

RIES

(

 

”717117111171 ii) Mil I1 @Iflffligfliflflllflfflfil