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This is to certify that the
thesis entitled

SHELTER, RESPIRATION RATES, AND PREY CONSUMPTION
AS FACTORS CONTRIBUTING TO DISPLACEMENT OF
MOTTLED SCULPIN (Cottus bairdl) BY ROUND GOBY (Apollonia
melanostomus) IN GREAT LAKES NEARSHORE AREAS

presented by
Janice Irene Sloan

has been accepted towards fulﬁllment
of the requirements for the

Master of degree in Department of Fisheries and
Science Wildlife

 

 

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6/07 p-lCIRC/DateDue‘indd-pj

SHELTER, RESPIRATION RATES, AND PREY CONSUMPTION AS FACTORS
CONTRIBUTING TO DISPLACEMENT OF MOTTLED SCULPIN (Cottus bairdi) BY
ROUND GOBY (Apollonia melanostomus) IN GREAT LAKES NEARSHORE AREAS

By

Janice Irene Sloan

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

2007

ABSTRACT

SHELTER, RESPIRATION RATES, AND PREY CONSUMPTION AS FACTORS
CONTRIBUTING TO DISPLACEMENT OF MOTTLED SCULPIN (Cottus bairdi) BY
ROUND GOBY (Apollonia melanostomus) IN GREAT LAKES NEARSHORE AREAS

By
Janice Irene Sloan

Great Lakes mottled sculpin (Cottus bairdi) populations appear to be declining in
response to round goby (Apollonia melanostomus) invasion of nearshore areas. I
conducted several laboratory experiments to evaluate the potential mechanisms and
consequences of this native ﬁsh displacement. First, I evaluated the respiration rates of
these two species as a function of shelter availability. Respiration rates were not
signiﬁcantly different between shelter and non shelter treatments for both species. In
addition, respiration rates were not signiﬁcantly different when the species were
compared by size regardless of treatment. Large mottled sculpin and round goby
respiration rates were signiﬁcantly greater than smaller ﬁsh of the same species. I also
conducted maximum consumption trials using amphipods as prey items. Surprisingly,
mottled sculpin consumed signiﬁcantly greater numbers of amphipods than round goby.
The larger ﬁsh consumed more amphipods than the smaller ﬁsh. Mottled sculpin and
round goby biology and ecology overlap making them competitors in the nearshore areas
of the Great Lakes. The results of this study suggest that round goby have the potential to
cause ecosystem-wide bioenergetic changes because although respiration rates are the
same as the mottled sculpin at similar sizes, round goby can grow larger and occur in

greater numbers, thereby generating greater metabolic demands compared to the native

mottled sculpin.

ACKNOWLEDGEMENTS
Funding for this project was provided by the Great Lakes National Program Ofﬁce of the
United States Environmental Protection Agency. The contents of this document do not
necessarily reﬂect the views and policies of EPA, nor does mention of trade names or

commercial products constitute endorsement or recommendation of use.

I want to thank my advisor, Reuben Gofor'th, for providing the much needed guidance to
complete this project. In addition I would like to thank my committee members Dan
Hayes and Thomas Burton, for their help and guidance from start to ﬁnish. I appreciate
the help and support of my labmates Brandon Armstrong, Holly Campbell, and Aly
Olesen. In addition, I want to thank Brandon Armstrong, and Bhavisha Bhalsod for the

use of their data.
I would like to thank my family for their support. Lastly, I would like to thank, my

husband who was always there to encourage me and give me the support I needed to

complete this thesis.

iii

TABLE OF CONTENTS

LIST OF TABLES .............................................................................................................. v
LIST OF FIGURES .......................................................................................................... vii
INTRODUCTION .............................................................. . ............................................... 1
METHODS ......................................................................................................................... 4
RESULTS ......................................................................................................................... 14
DISCUSSION ................................................................................................................... 27
APPENDICES .................................................................................................................. 34
LITERATURE CITED ..................................................................................................... 48

iv

LIST OF TABLES

Table 1. Chamber dimensions for respirometers used to estimate oxygen consumption by
mottled sculpin and round goby. Volumes of both the experimental chamber and the
entire apparatus (i.e., chambers, pump, tubing, etc.) are provided. .................................... 5

Table 2. Dimensions of shelters used in the respirometry trials. Shelters were constructed
of bisected commercially available polyvinyl chloride (PVC) couplers. ........................... 7

Table 3. Amphipods used in maximum consumption experiments by ﬁsh size class ...... 10

Table 4. Mean (:tSE) values for measured characteristics of mottled sculpin and round
goby. Adjusted weight is the wet weight of each ﬁsh minus the stomach wet weight to
adjust for differences in weight due to ingested amphipods in stomachs resulting from
maximum consumption trials ............................................................................................ 15

Table 5. MeaniSE (number of ﬁsh per cell, n) for each species by size class and
treatment. Research hypotheses and according contrast result * indicate research
hypotheses that are signiﬁcant at the 0.05 level. .............................................................. 21

Table 6. Descriptive data of maximum consumption experimental trials. Mean (:I:SE)
stomach wet weight, number of amphipods consumed, and size eaten for each species
and size class. Mean (iSE) size eaten was calculated with amphipods of known length
only. .................................................................................................................................. 26

Table A - 1. Descriptive characteristics of mottled sculpin and round goby used in
experimental trials ............................................................................................................. 35

Table A - 2. ANCOVA results for adjusted respiration (respiration rate during trial minus
daily bacterial respiration estimate) with total length as a covariate and species and
shelter as grouping factors. ............................................................................................... 36

Table A - 3. Mottled sculpin shelter treatment respiration data including water
temperature, YSI, and LaMotte measurements; estimated respiration minus biological
oxygen demand, and trial duration .................................................................................... 37

Table A - 4. Round goby shelter treatment respiration data including water temperature,
YSI, and LaMotte measurements; estimated respiration minus biological oxygen demand,
and trial duration. .............................................................................................................. 38

Table A - 5. Mottled sculpin non shelter treatment respiration data including water
temperature, YSI, and LaMotte measurements; estimated respiration minus biological
oxygen demand, and trial duration .................................................................................... 39

Table A - 6. Round goby non shelter treatment respiration data including water
temperature, YSI, and LaMotte measurements; estimated respiration minus biological

oxygen demand, and trial duration .................................................................................... 40
Table A - 7. Equations mentioned in text. ....................................................................... 41

Table A - 8. Standard Length, wet weight, and stomach contents of mottled sculpin from
western Lake Michigan. .................................................................................................... 43

vi

LIST OF FIGURES

Figure 1. a) Small respirometer with a centimeter scale, b) large chamber with shelter
located in back right corner and arrows indicating the location of the water circulation
ports, c) top view of large chamber with shelter located in back right corner and arrows
indicating the location of the water circulation ports, (1) small, medium, and large
respirometers side-by-side for comparison, and e) chamber set up for a shelter treatment
in acclimation stage with a mottled sculpin. The front water circulation port is connected
to the pump while the rear is not and the YSI probe is inserted in the top of the chamber.6

Figure 2. Sagittal otoliths of a) a round goby age 2+ and b) a mottled sculpin age 3+
arrows depict annuli. ......................................................................................................... 12

Figure 3. Mottled sculpin and round goby age vs. total length ........................................ 17

Figure 4. Mottled sculpin and round goby a) total length vs. adjusted weight, adjusted
weight equals total wet weight minus stomach wet weight to account for amphipods eaten
in maximum consumption trial, b) total length vs. adjusted respiration from respiration
trials includes both shelter and non-shelter treatments, adjusted respiration is the total
respiration minus respiration due to bacteria determined with predictive equations, and c)
total length vs. number of amphipods eaten per hour during maximum consumption
experimental trials ............................................................................................................. 18

Figure 5. Bacterial respiration vs. day of trial for small, medium, and large respirometers.
Equations based on the linear regression lines were used to estimate bacterial
consumption for ﬁsh respiration trials on each speciﬁc day ............................................. 20

Figure 6. Mean respiration rate (:tSE) a) within shelter treatment for both mottled sculpin
and round goby, b) within the non shelter trial for both mottled sculpin and round goby,
c) with treatments combined for mottled sculpin and round goby, d) between shelter and
non shelter treatments for mottled sculpin, and e) between shelter and non shelter
treatments for round goby. ................................................................................................ 22

Figure 7. Histogram depicting the total length distribution of amphipods consumed
during the maximum consumption trials by both mottled sculpin and round goby.
Unknown lengths (Unk*) reﬂect the number of amphipods that were mangled during
ingestion and therefore could not be measured accurately. .............................................. 24

Figure A - 1. Map of collection locations for mottled sculpin and round goby used in
experimental trials, the location of sites where mottled sculpin were collected for diet
study, and location of Calumet Harbor mentioned in other studies .................................. 45

Figure A - 2. YSI adjusted respiration rates vs. LaMotte respiration rates * indicates YSI

value that was substituted by the LaMotte adjusted respiration value. Adjusted
respiration is the ﬁsh respiration rate minus the estimated bacterial respiration rate. The

vii

line represents a 1:1 to agreement between the two methods of determining oxygen
concentration. .................................................................................................................... 46

Figure A - 3. Standard length (SL) a) vs. adjusted weight (AW=wet weight minus
stomach wet weight of mottled sculpin and round goby from experimental trials), b) wet
weight (WW) of mottled sculpin from southwestern Michigan streams, and c) wet weight
of mottled sculpin from western Lake Michigan. ............................................................. 47

viii

INTRODUCTION

The round goby, Apollonia melanostomus (Stepien et al. , 2006), is a Ponto-
Caspian benthic forage ﬁsh introduced into the Laurentian Great Lakes, most likely
through ballast water. Invasion of the nearshore areas of these lakes by round goby has,
in recent decades, been correlated with a sharp decline in mottled sculpin, Cottus bairdi,
populations, indicating a changing benthic ﬁsh community (Lauer et al. , 2004). The
implications of these changes are unclear, although recent studies indicate that
modiﬁcations of benthic - predator food web pathways are occuning (Dietrich et al. ,
2006; King et al., 2006; Truemper et al., 2006).

Round goby body size, diet, spawning habitat, and shelter requirements overlap
with those of the mottled sculpin, making them ecologically similar and thus likely
competitors in rocky nearshore zones (Dubs et al. , 1996). Dubs and Corkurn (1996)
suggested that round goby are likely to outcompete mottled sculpin due to their more
aggressive nature, better lateral line system for detecting prey, and ability to have
multiple broods per year. They also showed that mottled sculpin and round goby tended
to remain in shelters during daylight hours when alone or with a conspeciﬁc. Mottled
sculpin generally vacated shelters in the presence of round goby, suggesting that shelter
availability may be limiting for mottled sculpin in areas where round goby have invaded.

The importance of shelter and reﬁrgia on benthic ﬁsh can be substantial (Fischer,
2000). Burbot, Lota Iota, a Great Lakes benthic ﬁsh species, has 30% higher respiration
rate on pebble substrates without shelter compared to cobble substrates with shelter.
This ﬁnding suggests that adequate shelter can affect respiration rate of benthic ﬁshes. If

true for mottled sculpin, higher metabolic demands due to lack of shelter could negatively

impact their competitive vigor (Fischer, 2000). Nesting interference and displacement of
mottled sculpin ﬁ'om shelter by round goby may be contributing to the decline in mottled
sculpin populations due to recruitment failure and poor habitat availability (Dubs and
Corkum, 1996; Janssen et al., 2001). Evidence of mottled .sculpin population decline and
the establishment of the round goby in high abundances gives urgency to understanding
the bioenergetics of these species in the Lake Michigan nearshore ecosystem (J anssen
and Jude, 2001; Lauer et al., 2004).

The bioenergetics model of Lee et al. (2005) for the round goby was based on
round goby consumption and respiration rates for ﬁsh that were >60mm and primarily
fed on mussels, (i.e., Dreissena spp.). Small round goby (<60mm) tend to have diets
comprised of mobile invertebrate prey rather than mussels and have yet to be
incorporated into a bioenergetics model (Diggins et al., 2002). Also, preferred
consumption of dreissenids by large round goby may reﬂect decreased searching time
and increased success rate compared to mobile prey (Diggins et al., 2002; Janssen and
Jude, 2001). Consumption rates based solely on dreissenids are likely not representative
of the full range of inﬂuences that round goby metabolic demands can have on Great
Lakes nearshore zones (Diggins et al., 2002; French et a1. , 2001; Janssen and Jude, 2001;
Schaeffer et al. , 2005; Weimer et al. , 1999).

Among the few studies of mottled sculpin in the Great Lakes, Janssen and Jude
(2001) described the age, growth, and diet of mottled sculpin collected from Calumet
Harbor in southern Lake Michigan. They showed that age 0 ﬁsh were between 30mm
and 60mm long and age 1+ ﬁsh were greater than 60mm based on otolith analysis and

length correlations. Stomach contents of both large and small mottled sculpin consisted

mainly of amphipods and isopods. Crayﬁsh, cladocera, and diptera were also found in
the stomachs of these ﬁsh. In addition, French and Jude (2001) collected mottled sculpin
in the St. Clair River where caddisﬂies, crustaceans, and ﬁsh dominated the gut contents.
These studies provided rough characterizations of mottled. sculpin food habits, age, and
growth, but they did not produce an adequate understanding of the bioenergetic demands
of these ﬁsh.

The paucity of studies on Great Lakes mottled sculpin and the incomplete
understanding of round goby metabolic demands over multiple size classes and prey
types has resulted in large gaps in understanding the roles of these species in nearshore
zone bioenergetics. Given these information gaps, I tested the hypotheses that round
goby have a higher metabolic demand due to a more active lifestyle than mottled sculpin
and that shelter availability inﬂuences mottled sculpin respiration rates more than round
goby respiration rates. Further, I tested the hypothesis that round goby consume greater

numbers of mobile prey compared to mottled sculpin.

METHODS

Wild-caught mottled sculpin and round goby were used in respirometry and
consumption experiments to acquire parameters for metabolic requirements. Fish were
collected in mid-October 2006 and transported to holding facilities at Michigan State
University within four hours of capture. Mottled sculpin were collected with a backpack
electroshocker (Smith-Root Model #12) from Bear Creek, a small stream near Marshall,
MI. The same backpack electroshocker and hook and line were used to collect round
goby around shore structures in Lake Michigan near Manistee and Ludington, MI. Six
small (30-40mm), six medium (41-60mm), and six large (61-85mm) ﬁsh were collected
for each species. Fish were selected to give the largest range of lengths in each size class;
ﬁsh not selected for study were released unharmed.

Fish were kept in two large ﬂow-through holding tanks (213cm x 61cm x 56cm,
length x width x depth respectively, 530 operating liters), one for each species, at the
University Research Containment Facility on the campus of Michigan State University.
The ﬁsh were held captive for no longer than two months to encourage natural behavior
(Fischer, 2000). Fish were isolated in each tank using marked containers so that each
individual ﬁsh was associated with a unique code for identiﬁcation in experimental trials.
Fish were acclimated to a temperature of 11.0 (i0.S)°C, and a 12 hour light/ 12 hour dark
photoperiod for at least two weeks prior to use in respiration trials. Thawed, previously
frozen midge larvae (Chironomidae) were fed to ﬁsh once daily while being held.
Experiment #1: Respiration

Three custom respirometers were constructed, one for each size class (small,

medium, and large, Table 1, Figure l a-e). The diagonal length of each chamber was

approximately equal to 2X the upper length limit of the size class for which it was made
(e. g., the small size class upper limit was 40mm; therefore, the Chamber’s diagonal length
was 80mm). Therefore, each chamber was large enough to allow the ﬁsh to move but
small enough to both minimize increased respiration due to excessive movement and
allow for a decrease of at least 1.0 mg/L of oxygen within four hours after the start of an
experimental trial. Each respirometer had a water tight ﬁtting for a dissolved oxygen
probe (i0.2°C, i0.3mg/L, Yellow Springs Inc., Model YSI 55) and two ports for water
circulation via a circulating pump (Aqua Lifter, AW20, 13.25 liters/hour). Respirometers
were placed in blackened aquaria to prevent agitation by laboratory movements dining

trials.

Table 1. Chamber dimensions for respirometers used to estimate oxygen consumption by
mottled sculpin and round goby. Volumes of both the experimental chamber and the
entire apparatus (i.e., chambers, pump, tubing, etc.) are provided.

 

Chamber Apparatus

Diagonal Length W'd‘h He'gh‘ Volume Volume

 

mm mm mm mm

( ) ( ) ( ) r ) (mm (mm
Small 80 58 57 58 190 230
Medium 115 85 85 63 460 493
Large 165 120 118 62 880 943

 

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Three polyvinyl chloride (PVC) couplers (commercially available as 5/8, 7/8, and
1 1/4 inch) were bisected to act as simple shelters during respiration experiments (Table
2). These shelters were large enough to allow all ﬁsh in a given size class to be
concealed by the shelter but small enough that the ﬁsh could move ﬁeely in the chamber.

Shelters were placed in the chambers so that they were arranged as in Figure l b and c.

Table 2. Dimensions of shelters used in the respirometry trials. Shelters were constructed
of bisected commercially available polyvinyl chloride (PVC) couplers.

 

Length Width Height com"

 

D'
(mm) (mm) (mm) 1" me t"
(Inches)
Small 29 16 6 5/8
Medium 41 22 11 7/8
Large 58 35 12 1 1/4

 

Initially, ﬁsh were randomly assigned to either a shelter or non shelter treatment.
This was determined by writing the unique ﬁsh codes on identical pieces of paper and
drawing them randomly from a cup. After completion of its initially assigned treatment,
a ﬁsh was held a minimum of three days and use in the contrasting treatment therefore,
each ﬁsh was used twice, once in each treatment (i.e., shelter/ non shelter). This
experimental design resulted in two respiration measurements per ﬁsh.

Fish were fasted for at least 48 hours prior to being used in each experimental
trial. One ﬁsh was introduced into a chamber at a time and allowed to acclimate for at
least 10 minutes or until its gill movements were slow and even. During the acclimation
period, one water circulation port was disconnected, allowing water to ﬂow freely

between the aquarium and the chamber (Figure 1e). Directly before each trial began,

water was drawn from the chamber into a Winkler bottle and allowed to overﬂow for 10
seconds. At this time the system was closed and a timer started. A LaMotte dissolved
oxygen kit (i0.2mg/L) was used to measure the oxygen concentration of the water
sample. Oxygen concentration ($0.01mg/L), temperature (:l:0.1°C) and time of reading
were also recorded from the YSI probe after the meter had stabilized (i.e., 2-30 minutes
after the trial began). A second YSI reading was taken approximately 15 minutes after
the original reading, and the time was recorded. After four hours, ﬁnal YSI
measurements were made for oxygen concentration, temperature, and time of reading. A
second water sample was immediately extracted from the chamber to end the trial. The
extracted water sample was titrated with the LaMotte dissolved oxygen kit to determine
ﬁnal oxygen concentration. The ﬁsh were returned to the individual containers in the
holding tank at the conclusion of each experimental trial.

Although ﬁsh mobility in respirometers was limited, the experiments were
videotaped and reviewed to determine whether activity levels duringvthe trials may have
inﬂuenced respiration rates. Empty respirometers were also run for at least seven hours
once every 24 hours to evaluate bacterial respiration rate (BR) that was not due to ﬁsh
respiration. After each empty chamber trial was completed, the entire apparatus was
cleaned with cider vinegar and then thoroughly rinsed with distilled water.

Experiment #2: Maximum Consumption

Amphipods (Crustacea: Amphipoda) were used as mobile prey in maximum
consumption (MC) experiments for both mottled sculpin and round goby. These taxa
were chosen based on mottled sculpin gut contents reported by J anssen and Jude (2001).

Amphipods were collected one day prior to use in experimental feeding trials from a

marsh near East Lansing, MI. Amphipods were randomly placed in water ﬁlled bags in
quantities of 50, 75, or 100 individuals. The bags were incubated in the large tanks
holding the ﬁsh. Fish were fasted for 48 hours prior to experimentation.

Experiments were conducted at night due to reported nocturnal feeding behaviors
of mottled sculpin and round goby (Hoekstra et a1. , 1985; Janssen and Jude, 2001; Jude et
al. , 1995). Red light was used so that each ﬁsh could be videotaped. Three ﬁsh were
randomly selected by drawing three ﬁsh codes from a cup for each size class and species.
Fish were acclimated in small aquaria (3 L) incubated within a large blackened aquarium
to minimize water temperature ﬂuctuation and prevent agitation of ﬁsh due to laboratory
movements. Fish were acclimated for at least 10 minutes or until their gill movements
were slow and even. Once the ﬁsh had been acclimated, 50, 75, or 100 amphipods were
added to the aquaria according to ﬁsh size (Table 3). Fish were allowed to feed ad libitum
for one hour, then immediately transferred to an aquarium containing adequate amounts
of Tricane-S (Tricane methanesulfonate, Western Chemical Company) to euthanize the
ﬁsh (i.e., >150 mg/L). Fish were then frozen at -23°C and the stomach contents of each
ﬁsh were later inspected to determine number of amphipod consumed (AC, number of
amphipod/ stomach). While direct analysis of the stomach contents provided counts of

prey eaten, videotape reviews of each feeding trial provided data on prey capture rates.

Table 3. Amphipods used in maximum consumption experiments by ﬁsh size class.

 

 

Number of
F' b 8'

Is Ize Class Amphipo d
Small 50
Medium 75
Large 100

 

Somatic Measurements

After the respiration experiment, ﬁsh not used in the MC experiment were fasted
for 48 hours and then placed into an aquarium containing adequate amounts of Tricane-S
to euthanize the ﬁsh. Total length (TL), standard length, and wet weight (OHAUS,
AdventurerPro AV53, :I: 0.001) were measured for all ﬁsh used in the respiration trial. In
addition, all of the ﬁsh were dissected to retrieve otoliths, determine sex, and inspect
stomachs. A dorsal-ventral cut was made just anterior of the operculum to remove the
sagital otoliths from mottled sculpin and round goby (2 a and b). Otoliths were cleared

using a 10% bleach solution and ﬁxed on slides with thermoplastic glue (CrystalbondTM

509, Aremco Products Inc.). The otoliths were then polished using ultraﬁne sandpaper to
allow for easier detection of growth rings. Determination of age was conducted using a
Meiji dissecting microscope (model EMZ-13TR), a Scion Corporation camera, Scion
Visicapture software, and Image J 1.32j software.

Determination of sex was conducted using both external and internal dimorphic
characteristics. Gential papilla of both mottled sculpin and round goby were used as

external indicators of sex (Charlebois et al., 1997; Miller, 1984). Examination of internal

10

morphology involved removal of either the ovaries or testes and weighing them
($0.001 g).

In addition to the ﬁsh used in the experimental trials, length, weight, otoliths, and
stomach contents of 40 mottled sculpin from western Lake Michigan nearshore areas
(Kenosha, WI to Two Rivers, WI) were also analyzed. Fish were collected via nighttime
trawling at depths of 4-6m during the summer of 2005. Processing of these ﬁsh follows

techniques previously described.

11

 

arrows depict annuli.

Statistics

Statistical analyses were conducted using SPSS 15.0 (SPSS Inc.). Estimated BR
was subtracted from corresponding ﬁsh respiration rate resulting in adjusted ﬁsh
respiration rate (AR) estimates for each trial. Adjusted weight (AW) was calculated by
averaging three replicate weight measurements and subtracting stomach wet weight to
account for increased weight due to amphipod ingestion during MC trials. Non-linear
regression models were ﬁtted to AR and AW, while linear regressions were used to ﬁt
MC, BR, and age. Age and ntunber of amphipods eaten were evaluated using analysis of
variance (ANOVA) to determine differences between species. A posteriori Tukey’s
honestly signiﬁcant difference (HSD) comparisons were conducted when factors were
signiﬁcant in the ANOVA tests. Contrasts were used to examine speciﬁc hypotheses

related to respiration rates. An alpha of 0.05 was used to determine signiﬁcance.

l3

RESULTS

Eighteen mottled sculpin (6/size class) with a mean TL of 54:1:4mm and mean
adjusted weight of 1.884:t0.392g were used in the experiments (Table 4). Thirty three
percent of the mottled sculpin were females with an average gonad weight of
O.146:t0.049g, while male gonad wet weight averaged 0.052i0.030g (Table 4). Most
females were gravid with up to 9% of their adjusted weight represented by the ovaries
(Table 4).

Round goby proved to be much more difﬁcult to collect than anticipated, especially
the smaller size classes; therefore, six large, two medium, and six small ﬁsh were
available for the experimental trials (Table 4). However, three of the smallest round goby
were lost during the holding period, resulting in only three small round goby available for
use in experiments. Thus, a total of 11 round goby with a mean TL of 60:l:6mm and a
mean adjusted weight of 3.215i0.800g were used in the respiration experiments (Table
4). Forty-ﬁve percent of the round goby were females with a mean ovary weight of
0.145zt0.041g (Table 4). Up to 5% of the females’ adjusted weight was accounted for by

the ovaries (Table 4). Most females were found to be in a gravid condition.

14

 

 

 

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Ages determined from otolith annuli of both species ranged from O-4+ years.
Mottled sculpin age 1+ ﬁsh had a mean TL of 37i1mm (range: 35 to 40mm), age 2+ had

a mean TL of 56i5mm (range: 39 to 80mm), age 3+ ﬁsh had a mean TL of 65i12mm
(range: 52 to 77 mm), and one age 4+ had a TL of 83mm (TL=14.8*Age-24.5, R2=0.532,
Figure 3). Round goby were age 0+ with mean TL of 37i2mm (range: 32 to 37mm), age

1+ with mean TL of 49ilmm (range: 48 to 50mm), age 2+ with mean TL of 75i4mm

(range: 65 to 82mm), and an age 3+ ﬁsh measuring 80mm in TL (TL=17.7*Age-36.1,
R2=0.867, Figure 3). The AN OVA test indicated that mottled sculpin and round goby
lengths at age were signiﬁcantly different (F =1 1.8, p=0.005).

Allometric equations determined from a ﬁtted power curve for TL and AW for

mottled sculpin and round goby had coefﬁcients of determination of 0.991 and 0.999,

respectively (Figure 4). The resulting predictive equations were AW = 4.26*10-

O6TL3'190 for mottled sculpin and AW = 1.49"‘10-O6TL3'478 for round goby (Figure 4).

16

_ —-L'l Mottled Sculpin
A80 , ---A RoundGOby ‘ Q

570

l

“g
0\
O

I

 

 

 

Figure 3. Mottled sculpin and round goby age vs. total length.

17

a)
— a Mottled Sculpin
6 ‘ A Round Goby x“

Adjusted Weight (g)

 

P

Adjusted Respiration
(mg Oz/hou r)
O

 

 

Number of Amphipods

 

 

 

Total Length (mm)

Figure 4. Mottled sculpin and round goby a) total length vs. adjusted weight, adjusted
weight equals total wet weight minus stomach wet weight to account for amphipods eaten
in maximum consumption trial, b) total length vs. adjusted respiration from respiration
trials includes both Shelter and non-shelter treatments, adjusted respiration is the total
respiration minus respiration due to bacteria determined with predictive equations, and c)
total length vs. number of amphipods eaten per hour during maximum consumption
experimental trials.

18

Respiration

BR was estimated for each day based on ﬁtted equations for the small

(BR=0.003*Day-0.018, R2=0.827), medium (BR=0.003*Day, R2=0.462), and large

(BR=0.009*Day-0.066, R2=0.840) chambers separately (Figure 5). A total of 34 BR

trials were conducted. In addition, inspection of the intestines and stomachs of ﬁsh not

used in the MC experimental trials veriﬁed that 48 hours was an adequate fasting period

to fully evacuate food from the digestive tract of both mottled sculpin and round goby.
A total of 64 respiration trials were conducted, including both non-shelter and

shelter treatments. Regressions for mottled sculpin and round goby AR vs. TL resulted in

2.727

coefﬁcients of determination of 0.832 (AR=2.86*10.6*TL ) and 0.914 (AR=4.76*10-

6 2.600 . . . . .
*TL )for ower curves res ctIvel (F 1 ure 4). Res IratIon rates were estimated
P P6 Y 8 P

using YSI measurements with one exception in which YSI equipment error was
suspected; thus, the LaMotte measurements were used in place of the YSI readings in that
case.

Round goby and mottled sculpin respiration rates were not signiﬁcantly different
within size classes for the trials with shelter provided (F=0.117, p=0.734, Table 5, Figure
6a). Similarly, respiration rates were not statistically different between comparably sized
round goby and mottled sculpin for the non shelter treatment (F=0.071, p=0.791, Table 5,
Figure 6b). Mottled sculpin respiration rates were not signiﬁcantly different between
treatments among the three size classes (F=0.149, p=0.701, Table 5, Figure 6d). The
round goby was also not signiﬁcantly different between treatments within each of the

three size classes (F =0.043, p=0.837, Table 5, Figure 6e). When the data were combined

19

0.20

0.15

0.05

Bacterial Respiration Rate
(mg Ozlhou r)
O
8

0.00

—-A Large
-- D Medium
—<> Small A .x"

 

 

 

5 10 15 20 25
Day

Figure 5. Bacterial respiration vs. day of trial for small, medium, and large respirometers.
Equations based on the linear regression lines were used to estimate bacterial
consumption for ﬁsh respiration trials on each speciﬁc day.

20

 

 

Se... m»... 2...... 02...... :0... 2.2. 2.....2 2...» .25....

 

.........v 2...... . a... =2... 2.... 2...... 2......2 a; .2. a»...
.........v 8...... .2. 00.... .3... 2.. 2......2 a.» a»... 2.....02
m»... S... .2. 2202.. 2.. 5.... 22 2......2 a.» .2. =2.»
R»... 2...... 2.253.. 2.2... 2.. a. 2.. 2......2 =2. 2...» 8......
.8... I 0...... 2.252. 2.2.. 2.. a. 2.2 2......2 522......» 02.2.2
.8... .2... 2.22.. 2.2... 28...... 2...» .25.... :0... 22.. 2......2 a: 0......O. 022...).
.00... 2.... 2.22.. 2.2.... .0... 2......» 02.2.... .3... 22.. 2....2 =2 2...» 0.5....
05.0.1. 02.0.»... 2350...»: 5.803% ﬂ

 

 

AN 5 98.3.05”... .3 8:522... G. 3:52.36 .2. emc.¢ﬂa~v.= an: c8623.... AN: 986.32.... 60:38.5

 

G. .3300»... .N. 80.32.... G. 80.3%.... G. .2300»... G. .833... G. .m.....#....... 2.2.» .82

 

 

 

G. 303...... G. 2.0.3....» G. $0.30»... G. 30.3.2... G. .330...» G. .330»... ..2.2.»
030.— 8=_..0.>. =08m 030:— 85802 =08m 808.00.;
2...... 0.5.... 2......» 022....
800.). .0830... .80 :00

 

.26. no... 0... .0 800.8%.» 0.0 .0... »0»0...0....... ..0..00»0.. 0.00.0... .. ....»0. .»0.800
8.80000 .80 »0»0...0...... ..0.00»0y. 808.00.. .80 »»0.0 00.» .3 8.00..» ..000 20.. A: ...00 20.. a»... .0 .388. m.m800.>. .m 030...

a) d)

  

 

 

 

 

 

 

 

 

0‘6 ‘ lMottled Sculpin 0‘6 llShelter
l Round Goby 0 Non Shelter

0.4 - 0.4 3
A 0.2 ‘ 0.2 ‘
r.
5 ﬂ
3 0,0 - 0.0 ‘
ON Small Medium Large Small Medium Large
an M e)
V 0'6 ' BMottled Sculpin 0'6 'IShelter
g I Round Goby 0 Non Shelter
'5 0.4 r 0.4 4
.2
g; 0.2 . 0.2 «
2 E1
5 0.0 - - I 0.0 -—ﬁJ‘ -
E Small Medium Large Small Medium Large

c)

0‘6 7 BMottled Sculpin

lRound Goby
0.4 *

 

 

 

0.2 3 i
0.0 -
Small Medium Large

Size Class

Figure 6. Mean respiration rate (iSE) a) within shelter treatment for both mottled sculpin
and round goby, b) within the non shelter trial for both mottled sculpin and round goby,
c) with treatments combined for mottled sculpin and round goby, d) between shelter and
non shelter treatments for mottled sculpin, and e) between shelter and non shelter
treatments for round goby.

22

according to species and treatment, the large size class had signiﬁcantly greater
respiration rates than the medium and small size classes (F=43.968, p<0.00l, and
F=72.983, p=<0.00l, Table 5, Figure 6c). However, the medium and small size classes
were not signiﬁcantly different from each other (F=1.169, p=0.285, Table 5, Figure 6c).
Round goby respiration rates were not signiﬁcantly different from mottled sculpin
respiration rates across sizes and treatments (F=0.185, p=0.669, Table 5, Figure 6c).

Analysis of ﬁsh movements from video tapes veriﬁed that activity was not
signiﬁcantly different between species (F=l .592, p=0.217), size class (F=0.187,
p=0.830), and shelter availability (F=O.421, p=0.521). One interaction in the ANOVA
was signiﬁcant, species and class (F =5.800, p=0.007).

Consumption

Three ﬁsh from each size class and species were used in the MC trials except for
the medium round goby size class which only contained two ﬁsh, resulting in 17 total
MC trials. Analysis of western Lake Michigan mottled sculpin veriﬁed a diet dependent
on crustaceans, mainly isopods which were found in 89% of the stomachs with an
average of 6. l 3 individuals per stomach. Oligochaeta (73% of stomachs) and
Chironomidae (53% of stomachs, Diptera) were the next most abundant taxa, with the
remaining taxa represented in less than 10% of the ﬁsh.

A total of 467 amphipods were eaten during the experiment, where 98% were
Hyalellidae and 2% were Gammaridae with no amphipods larger than 6.5 mm in TL
(Figure 7). The lengths of some amphipods could not be measured because they were
mangled when ingested. In reviewing the video tapes from the experimental trials it was

difficult to differentiate between attempts at amphipods and normal movements therefore

23

p—s

N

G
l

3

.§.100~

280*

a

<

z 60*

2

a 40—

3

z 20
0

 

   

Unk* 2.5 3 3.5 4 4.5 5 5.5 6 6.5
Total Length (mm)

Figure 7. Histogram depicting the total length distribution of amphipods consumed
during the maximum consumption trials by both mottled sculpin and round goby.
Unknown lengths (U nk“) reﬂect the number of amphipods that were mangled during
ingestion and therefore could not be measured accurately.

24

these data were not analyzed.

The AC by ﬁsh in each trial ranged from 0-96 individuals. Comparisons of MC

between the two species indicated that mottled sculpin (AC=1 .3 l *TL-3 7.2, R2=O.639)

consumed signiﬁcantly greater numbers of amphipods compared to round goby

(AC=0.56*TL-20.6, R2=O.741) (F=l3.54, p=0.005 Table 6 and Figure 4c). Size class was

also signiﬁcantly different, although the interaction between size class and species was
not signiﬁcant (F=11.26, p=0.002 and F =1 .475, p=0.27l, respectively). Separate a
posteriori comparisons indicated that for the mottled sculpin there was signiﬁcant
difference between only the large and small size classes (p=0.027) and results of the

round goby comparison were similar (p=0.034).

25

Table 6. Descriptive data of maximum consumption experimental trials. Mean (:SE)
stomach wet weight, number of amphipods consumed, and size eaten for each species
and size class. Mean (:tSE) size eaten was calculated with amphipods of known length
only.

 

Stomach Wet Number of Size Eaten

 

 

Weight (g) Amphipod (mm)
Mottled Sculpin 9 0191:0335 34:7 45:01
Small 3 0353:0302 11:1 43:0.1
Medium 3 0163:0324 29:5 4.4:0.1
Large 3 0350:0344 63:12 45:01
Round Goby s 0.066:I:0.022 11:4 42:02
Small 3 0.006:I:0.005 1:1 43:03
Medium 2 0333:0311 5:2 33:02
Large 3 0174:0318 25:5 43:0.2

 

26

DISCUSSION

The ecology of Great Lakes nearshore zones is being transformed as the native
mottled sculpin is displaced by the invasive round goby. The potential consequences of
this transformation are many, including alteration of biological pathways and demands.
Insight into the impacts of this shift can be gained via comparison of mottled sculpin and
round goby bioenergetics. While it was not surprising that smaller ﬁsh of both species
consumed less oxygen than larger ﬁsh of the same species, the results demonstrated that
neither round goby nor mottled sculpin respiration rates differed based on the presence or
absence of shelter. In addition, when species were compared, mottled sculpin and round
goby of similar size did not signiﬁcantly differ in their respiration rates in either the
shelter or non shelter treatments. Lastly, mottled sculpin consumed more amphipods
when fed ad libitum than round goby of comparable size. These results were largely
unexpected and have some interesting implications for interpreting nearshore ecosystem
responses to shiﬁs in benthic ﬁsh composition from mottled sculpin to round goby.
Respiration

The lack of observed shelter effects on respiration rates of mottled sculpin and
round goby was very surprising. Previous laboratory studies have found Shelter to be
important to both species, especially during spawning (Belanger et al., 2003; Dubs and
Corkum, 1996; Janssen and Jude, 2001). Further, respiration rates of obligate benthic
ﬁshes have been shown to be dramatically inﬂuenced by shelter availability in at least
one Great Lakes conspeciﬁc species, the burbot (Fischer, 2000). While my results

suggest that cover availability does not inﬂuence respiration rates in either species, there

27

may be several reasons for the lack of this effect in the experiments described herein.
Among these, equipment sensitivity, the type of shelter provided, the lengths of the trials,
and BR in the chambers are experimental design factors that may have inﬂuenced the
lack of response between shelter/non shelter treatments for both species. (Belanger and
Corkum, 2003; Lee and Johnson, 2005). Even though the potential effects of these
experimental design elements were not explicitly tested in this study, it is unlikely that
any of these factors signiﬁcantly inﬂuenced respiration rates in either species. Although,
BR in the large chamber was greater than the other chambers, it is reasonable to assume
that the larger Chamber’s foam seal, the most difficult portion of the chamber to clean,
represented a larger surface area than in the other two chambers and was responsible for
this difference in BR. Regardless, differences in BR were accounted for and it is unlikely
that it signiﬁcantly inﬂuenced the ﬁsh respiration rates.

The absence of changes in respiration rates by both Species may have also been
due to ecological factors not included in the experimental design. Attempts to maintain
natural behavior in my experiments may have been simply ineffective and resulted in a
decreased response in mottled sculpin and round goby (Fischer, 2000). Stream mottled
sculpin behavior may have varied from counterparts in the Great Lakes nearshore area in
regards to importance of Shelter and predatory pressures. This factor was not evaluated
here due to availability of ﬁsh and is not deemed to signiﬁcantly affected results.
Additional studies examining the differences between stream and Great Lakes nearshore
mottled sculpin are need to understand behavior differences between these populations.

Predator cues and conspeciﬁcs were not provided in this experiment, therefore it

is reasonable to conclude that shelter availability alone does not inﬂuence respiration

28

rates in either mottled sculpin or round goby. Therefore, lack of Shelter habitat alone
may not be as stressful as originally hypothesized. Additional experimental trials that
include the presence of predator cues or conspeciﬁcs as ecological factors are needed to
determine whether respiration rates in mottled sculpin and round goby vary according to
shelter availability under such conditions.

Another reason that round goby, in particular, may not have exhibited changes in
respiration rates between shelter and non shelter treatments is that this species is thought
to have greater ecological plasticity compared to the mottled sculpin. Round goby are
often found in habitats lacking shelter, especially small round goby, due to occupation of
preferred rocky habitats by mature adults (Ray et al. , 2001). Therefore, it is reasonable to
expect that shelter availability may not strongly inﬂuence respiration rates in this species.
To try to account for this, the round goby used in the respirometry trials in this study
were collected from rocky habitats. However, these individuals showed no change in
respiration rates in response to shelter availability despite their capture in rocky habitats.
While the proposed greater ecological plasticity of the round goby may give them greater
competitive advantages compared to mottled sculpin in some respects, it does not appear
that shelter availability alone provides any kind of advantage to round goby with respect
to respiration rates. However, competitive interactions between round goby and mottled
sculpin may induce greater respiration rates in mottled sculpin, and experimental trials to
evaluate these potential effects are needed.

Despite predictions that round goby would have greater respiration rates than
mottled sculpin, there was no statistically signiﬁcant difference between the two Species

for either treatment. This suggests that the basic metabolic demands of these ﬁsh are

29

similar at comparable sizes. However, similarly sized ﬁsh are not of comparable ages for
the mottled sculpin and round goby. According to unpublished data, mottled sculpin
found in southern Michigan streams were up to 84mm in standard length and 4+ years of
age (B. Armstrong pers. comm), while mottled sculpin in western Lake Michigan were
up to 79mm in standard length and 4+ years of age (J. Sloan and B. Bhalsod pers.
comm). In contrast, round goby estimated to be 4+ years old have been found up to 124
mm TL in the Detroit River and 140+mm TL in Calumet Harbor in southwestern Lake
Michigan (Charlebois et al. , 1997; MacInnis et al., 2000). Round goby ages and lengths
observed in this study were consistent with the published data based on round goby from
the Detroit River (MacInnis and Corkum, 2000). This suggests that round goby can grow
40%+ larger than mottled sculpin despite similar life expectancies. Based on
respirometry results, it is reasonable to expect that round goby of these greater sizes
would have greater respiration rates than similarly aged, but considerably smaller,
mottled sculpin. Given this assumption, it can be expected that the bioenergetics of Great
Lakes nearshore areas are therefore likely to change even with a 1:1 replacement of

mottled sculpin with round goby. However, while mottled sculpin densities in Lake

Michigan have been reported from 0.06-0.77ﬁsh/m2, round goby have been reported in

densities from 03-40 ﬁsh/m2, indicating that round goby can occur in much greater

densities (Janssen and Jude, 2001; Janssen et al., 1985; Ray and Corkum, 2001). This
indicates that displacement is greater than 1:] and when combined with larger size at age
the round goby population is likely to have a greater bioenergetic demand than the
mottled sculpin population that it is replacing.

Consumption

30

The results of the MC trials were surprising in that they indicated that mottled
sculpin consumed a greater number of amphipods during the one hour feeding trial
compared to the round goby. This seems counterintuitive given that round goby grow to
a larger size in less time than the mottled sculpin (i.e., larger metabolic demand due to
increased somatic and gonad growth). There are several possible reasons for these
unexpected results. First, differential feeding strategies and/or patterns may have
inﬂuenced the abilities of mottled sculpin and round goby to eat during the experimental
feeding trials. Mottled sculpin are considered to have nocturnal or crepuscular feeding
habits, remaining hidden and largely inactive during daylight hours (Hoekstra and
Janssen, 1985). In contrast, round goby are frequently observed throughout the day (J.
Sloan, pers. obs.) and are suspected to eat throughout the day and night, especially large
goby that eat driessenid mussels (Ray and Corkum, 2001). This suggests that mottled
sculpin have adapted to forage in Short durations while round goby are able to forage
throughout the day. Thus, mottled sculpin may have consumed more amphipods during
the trials compared to the round goby because mottled sculpin are more accustomed to
eating in short durations during low or no light conditions. Fasting prior to the
experimental trials may have thus been ineffective at encouraging MC in both species
with behavioral cues overriding hunger in these individuals.

Experimental conditions may have also inﬂuenced consumption rates. Red light
used to video tape trials may have positively inﬂuenced the mottled sculpin, allowing
individuals to visually feed on the amphipods rather than relying principally on lateral
line detection, thereby foraging more effectively than if in no light conditions (Coombs et

al. , 2001; Coombs et al. , 2000; Hoekstra and Janssen, 1985; Janssen et al. , 1998; Kanter

31

et al. , 2003). One medium and one large mottled sculpin consumed over 50% of the
available amphipods during the one hour trial, and therefore their consumption may have
been limited by the depletion of prey items. However, when mottled sculpin were
examined their stomachs appeared full, so it is unlikely that substantial increases in
consumption would have been possible even if prey densities remained unchanged
throughout the experimental trial.

Similar to the mottled sculpin, it is unlikely that the red light signiﬁcantly
inﬂuenced round goby MC estimates. Round goby have a highly developed lateral line
system that allows this species to efﬁciently forage under low or no light conditions
(Diggins et al., 2002; Dubs and Corkum, 1996). In addition, it has been shown that
round goby foraging efficiency for amphipods only slightly diminishes in dark or turbid
conditions (Diggins et al., 2002). Therefore, the red light used herein may have had a
slight positive effect on MC estimates, but it is unlikely that it signiﬁcantly inﬂuenced the
results. In a study by Diggins et al. (2002), estimation of large round goby MC using
fewer prey items in a larger tank under ambient conditions produced comparable results
to those presented here for the same sized round goby. They also concluded that the
predominance of dreissenids in larger round goby diets may be the result of low
encounter rates with mobile prey and not necessarily a preference for them. Therefore, it
is unlikely that mobile prey would negatively affect round goby MC during the high
encounter rates experienced in the trials.

Conclusions
The round goby is an adaptable invader that is contributing greatly to a changing

Great Lakes ecosystem. Changes in benthic ﬁsh community species composition due to

32

this invader are thought to negatively impact native species such as the mottled sculpin as
well as altering food web structure. While it is generally suspected that round goby
negatively affect mottled sculpin due to competition for shelter, my study suggests that
shelter alone does not inﬂuence respiration rates in either species. Although my study
indicates that similarly sized round goby and mottled sculpin have statistically Similar
respiration rates, they are not of similar age. This suggests that round goby metabolic
demands are likely to be greater than adult mottled sculpin at comparable ages. Further
study of the effects of shelter on the respiration rates of these species in the presence of
conspeciﬁcs and predators is needed to better understand the dynamics between these
species in the wild. In addition, feeding strategies of both Species need to be evaluated to

more fully understand the metabolic requirements of the mottled sculpin and round goby.

33

APPENDICES

34

Table A - 1. Descriptive characteristics of mottled sculpin and round goby used in

 

 

 

 

 

 

 

 

 

experimental trials.
Total Standard Wet , Stomach Number of
Species Length Age Length Weight 11:41:;th 3°33“; Wet Amphipods
(mm) (mm) (g) "g (3) "g (3 Weight (g) Eaten
Mottled Sculpin
39.0 2+ 32.0 0.514 0514 Male 0.003 - -
40.0 1+ 32.0 0549 0549 Male 0.000 - -
Small 375 1+ 30.0 0.501 0.501 Female 0.005 - -
365 1+ 29.5 0.456 0398 Female 0.003 0.058 13
35.5 1+ 28.5 0377 0331 Male 0.002 0.046 11
36.0 1+ 28.0 0387 0333 Female 0.003 0.054 8
40.5 2+ 325 0.642 0.642 Male 0.000 - -
57.0 2+ 48.0 1.963 1.963 Male 0.017 - -
Meanm 51.0 2+ 41.0 1269 1.174 Female 0.040 0.095 16
525 3+ 42.5 1577 1383 Male 0.019 0.194 32
43.5 2+ 35.0 0.724 0.724 Male 0.003 - -
565 2+ 46.0 1.799 1599 Male 0.024 0200 38
77.0 3+ 63.5 4.449 4.449 Female 0372 - -
72.0 2+ 60.0 4.744 4.266 Male 0.036 0.478 96
L” c 68.5 2+ 56.5 2.854 2.854 Male 0.041 - -
g 80.0 2+ 65.0 5203 5.203 Male 0.452 - -
82.5 4+ 68.0 5.147 4.832 Female 0.452 0.315 49
66.5 - 54.0 2.958 2.683 Male 0.036 0275 44
RoundGoby
32.0 0+ 255 0.242 0.241 Jnknow; 0.001 0.001 0
Small 40.0 0+ 33.0 0.536 0521 Female 0.001 0.015 2
37.0 0+ 31.0 0.438 0.437 Female 0.001 0.001 0
, 495 1+ 41.5 1230 1.208 Male 0.004 0.022 3
Metium
485 1+ 39.5 1225 1.181 Male 0.054 0.044 6
80.5 2+ 67.0 6.199 6.103 Male 0310 0.096 15
65.0 2+ 54.0 3.115 3.115 Male 0.135 - -
L” c 81.0 2+ 68.0 6.492 6311 Female 0226 0.181 36
g 67.5 2+ 56.5 3.428 3.428 Jnknow. - - -
82.0 2+ 70.0 6.591 6.591 Female 0210 - -
80.0 3+ 67.0 6.397 6232 Female 0287 0.165 20

 

35

Table A - 2. ANCOVA results for adjusted respiration (respiration rate during trial minus

daily bacterial respiration estimate) with total length as a covariate and species and

shelter as grouping factors.

 

AN COVA Results for Adjusted Respiration

 

 

 

 

 

 

 

Source Type III Sum of Squares df _ Mean F Sig.
Mode 1* 4.470 5 0.894 82.32 0.000
Total Length 1.625 1 1.625 149.61 0.000
Species 0.003 1 0.003 0.28 0.597
Shelter 0.005 1 0.005 0.47 0.496
Species )1 Shelter 0.000 1 0.000 0.01 0.911
Error 0.576 53 0.011
Total 5.046 58
* R Squared = .866 (Adjusted R Squared = .875)
dfl 1112 F Sig.

Levene's Test of Equality of Error Variances 3 54 0.818 0.490
Factor Levels N
Species Mottled Sculpin 36

Round Goby 22
Shelter Shelter 29

Non Shelter 29

 

36

 

 

 

 

37

Non: 3:: NM .: c: a. . ::.::"v 2.: mNnv:u: mo:— :...
:2: Na: 3:: n... :.:. 9N.::.v .5... hm. . .u: N...:. ... .
me: :Nn: :::: a: v... ::.:..v 3.: 326...: n .... N... out...
I. ..: .:.: 8:: w: h:— :mum:.v «N... :93”: .m:. ....
:::.: NV: 3:: m: n. N. ::.::.v ::.: ::H . .u: m... . N.. .
3m: 3m: m.:: m: 0:. :..::.v on: .NnmNu: :N... m...
3:: N.N.: .m:.: a... :... 23:3. mm: :m....: 3.... :...
v. N: 3:: bN:.: :.: :.. . MNHN:3 :5: 53...: ....:. m. .
.:..: n:...: 3:: m: 5:. 35:3 ...: $5.“: 5:. .... 5.5.8).
:9 ..: 3:: 93.: v: ::. emuamum .3: ::3.:.: E: n. . .
a . ..: mN ..: 3:: h: :... NM. :3. 9:: 3.3:": Nn.:. ....
3:: m: ..: .N:.: N: . :.. . ::.: .3. 2.: ::.::u: an: 9.. .
:n:.: 3:: 2:: a: ::. :N. .:.v 2.: manna: 3:. N...
3:: 3:: 53.: v: :. . . ::”::.v 3.: :15”: N:.: m. . .
.N:.: :m:.: 93.: :.:. :.:. 3.. .:.v ::.: ::.N:.: .n.:. N.. . :55
:m:.: 5:: :::.: :.:. N. .. 3.3:... 2.: h .u. .u: :v... 5.. .
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42

Table A - 8. Standard Length, wet weight, and stomach contents of mottled sculpin from
western Lake Michigan.

 

Standard Wet

 

 

 

Site Length Weight Empty lsopoda Oligochaeta Chironomidae Copepoda Cladocera Diptera
Stomach
(mm) (a)
Two Rivers
31 1.032 3 1 8
41 1.301 1 1 8
41 1.206 15
44 1.710 3 3
51 2.858 I 17 64 1
52 2.989 5 1 4
53 2.953 1 1 1 6
54 3.171 2 5 2 1
56 3.575 1
69 6.831 1 6
79 12.493 2 16
Point Beach
58 4.273 2 1
Cleveland
34 0.765 3 2
35 0.749 1 2
36 0.950 3
38 1.144 2 1
40 1.412 10 3 2
41 1.252 1
42 1.221 9 2 5
43 1.671 6 2 1
45 2.028 1 2
46 2.418 5 2
47 2.387 11 1 3
49 1.731 5 2
57 3.883 8 1 4
59 4.133 4 8
60 4.871 9 2 1
61 4.741 13 6 1

 

43

Table A - 8. Continued.

 

Standard Wet

 

 

 

 

 

Site Length WEight Empty lsopoda Oligochaeta Chironomidae Copepoda Cladocera Diptera
Stomach
(mm) (s)
Sheboygan Point
20 0.143 9 1 1
21 0.181 3 1
39 1.308 2 2
50 2.333 13
63 6.015 10 11
67 7.006 34 9
Kohler-Andrae State Park _
48 2.302 5 2 1
73 6.852 6 7
Port Washington
33 0.651 2
55 3.464 7 4 1
62 4.806 25 6
Fox Point
51 2.325 1 1 3
54 2.972 9 3 2
South Milwaukee
- - 1
- - 8
- - 5 2

 

 

 

 

 

 

 

 

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45

ElMottled Sculpin
A Round Goby

    

(mg Oz/hour)

 

 

LaMotteAdj usted Respiration

T l

-0.2 0.0 0.2 0.4 0.6 0.8 1.0

YSI Adj usted Respiration (mg Oz/hour)

Figure A - 2. YSI adjusted respiration rates vs. LaMotte respiration rates * indicates YSI
value that was substituted by the LaMotte adjusted respiration value. Adjusted
respiration is the ﬁsh respiration rate minus the estimated bacterial respiration rate. The
line represents a 1:1 to agreement between the two methods of determining oxygen
concentration.

46

00
J

a)

A — El Mottled Sculpin
AW=7.5 7* 1 0'6*SL3'24
_ - - - A Round Goby

AW=2.92"‘10‘6"‘SL3-49

  
 
    

Adjusted Weight (g)
{3 3 "‘

 

 

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OOOWO\\O
l

v—In—s
QWNU‘
1;

Wet Weight (g)

 

 

 

u—ar—nu—s
NUIOOOUJ

Wet Weight (g)

 

 

OWONO

 

Standard Length (mm)
Figure A - 3. Standard length (SL) a) vs. adjusted weight (AW=wet weight minus
stomach wet weight of mottled sculpin and round goby from experimental trials), b) wet
weight (WW) of mottled sculpin from southwestern Michigan streams, and c) wet weight
of mottled sculpin from western Lake Michigan.

47

LITERATURE CITED

Belanger, R. M., and L. D. Corkum. 2003. Susceptibility of tethered round gobies

(Neogobius melanostomus) to predation in habitats with and without shelters.
Journal of Great Lakes Research, 29(4): 588-593.

Charlebois, P. M., J. E. Marsden, R. G. Goettel, R. K. Wolf, D. J. Jude, and S. Rudnicka.

1997. The round goby, Neogobius melanostomus (Pallas), a review of European
and North American literature: Illinois Natural History Survey.

Coombs, S., C. B. Braun, and B. Donovan. 2001. The orienting response of Lake
Michigan mottled sculpin is mediated by canal neuromasts. Journal Of
Experimental Biology, 204(2): 337-348.

Coombs, S., J. J. F inneran, and R. A. Conley. 2000. Hydrodynamic image formation by
the peripheral lateral line system of the Lake Michigan mottled sculpin, Cottus
bairdi. Philosophical Transactions Of T he Royal Society Of London Series B-
Biological Sciences, 355(1401): 1111-1114.

Dietrich, J. P., B. J. Fvlorrison, and J. A. Hoyle. 2006. Alternative ecological pathways in
the Eastern Lake Ontario food web-round goby in the diet of lake trout. Journal of
Great Lakes Research, 32(2): 395-400.

Diggins, T. P., J. Kaur, R. K. Chakraborti, and J. V. DePinto. 2002. Diet choice by the
exotic round goby (Neogobius melanostomus) as inﬂuenced by prey motility and
environmental complexity. Journal of Great Lakes Research, 28(3): 411-420.

Dubs, D. O. L., and L. D. Corkum. 1996. Behavioral interactions between round gobies

(Neogobius melanostomus) and mottled sculpins (Cottus bairdi). Journal of Great
Lakes Research, 22(4): 838-844.

Fischer, P. 2000. An experimental test of metabolic and behavioural responses of benthic

ﬁsh species to different types of substrate. Canadian Journal of Fisheries and
Aquatic Sciences, 57(11): 2336-2344.

French, J. R. P., and D. J. Jude. 2001. Diets and diet overlap of nonindigenous gobies and
small benthic native ﬁshes co-inhabiting the St. Clair River, Michigan. Journal of
Great Lakes Research, 27(3): 300-311.

Hoekstra, D., and J. Janssen. 1985. Non-visual feeding behavior of the mottled sculpin,
Cottus bairdi, in Lake Michigan. Environmental Biology of Fishes, 12(2): 111-
117.

Janssen, J ., and J. Corcoran. 1998. Distance determination via the lateral line in the
mottled sculpin. Copeia(3): 657-662.

48

J anssen, J ., and D. J. Jude. 2001. Recruitment failure of mottled sculpin Cottus bairdi in
Calumet Harbor, Southern Lake Michigan, induced by the newly introduced
round goby Neogobius melanostomus. Journal of Great Lakes Research, 27(3):
319-328.

J anssen, J ., and T. J. Quinn. 1985. Biota of the naturally rocky area of southwestern Lake
Michigan with emphasis on potential ﬁsh prey. In F. M. D'Itri (Ed), Artiﬁcial
reefs: marine and ﬁeshwater applications (pp. 431-442). Chelsea, MI: Lewis
Publishers, Inc.

Jude, D. J ., J. Janssen, and G. Crawford. 1995. Ecology, distribution, and impact of the
newly introduced round and tubenose gobies on the biota of the St. Clair and
Detroit Rivers. In M. Munawar, T. Edsall & J. Leach (Eds), The Lake Huron
ecosystem: ecology, fisheries and management (pp. 447-460). The Netherlands:
Ecovision World Monograph Series, S.P.B. Academic Publishing.

Kanter, M. J ., and S. Coombs. 2003. Rheotaxis and prey detection in uniform currents by
Lake Michigan mottled sculpin (Cottus bairdi). Journal Of Experimental Biology,
206(1): 59-70.

King, R. B., J. M. Ray, and K. M. Stanford. 2006. Gorging on gobies: beneﬁcial effects
of alien prey on a threatened vertebrate. Canadian Journal of Zoology-Revue
Canadienne De Zoologie, 84(1): 108-115.

Lauer, T. E., P. J. Allen, and T. S. McComish. 2004. Changes in mottled sculpin and
johnny darter trawl catches after the appearance of round gobies in the Indiana

waters of Lake Michigan. Transactions Of The American Fisheries Society,
133(1): 185-189.

Lee, V. A., and T. B. Johnson. 2005. Development of a bioenergetics model for the round
goby (Neogobius melanostomus). Journal of Great Lakes Research, 31(2): 125-
134.

MacInnis, A. J ., and L. D. Corkum. 2000. Age and growth of round goby Neogobius
melanostomus in the Upper Detroit River. Transactions of the American
Fisheries Society, 129: 852-858.

Miller, P. J. 1984. Tokology of gobies. In G. W. Potts & R. J. Wootton (Eds), Fish
Reproduction. London: Academic Press, Ltd.

Ray, W. J ., and L. D. Corkum. 2001. Habitat and site afﬁnity of the round goby. Journal
of Great Lakes Research, 27(3): 329-334.

Schaeffer, J. S., A. Bowen, M. Thomas, J. R. P. French, and G. L. Curtis. 2005. Invasion
history, proliferation, and offshore diet of the round goby Neogobius
melanostomus in western Lake Huron, USA. Journal Of Great Lakes Research,
31(4): 414-425.

49

Stepien, C. A., and M. A. Turneo. 2006. Invasion genetics of Ponto-Caspian gobies in the
Great Lakes: a 'cryptic' species, absence of founder effects, and comparative risk
analysis. Biological Invasions, 8: 61-78.

Truemper, H. A., T. E. Lauer, T. S. McComish, and R. A. Edgell. 2006. Response of
yellow perch diet to a changing forage base in southern Lake Michigan, 1984-
2002. Journal of Great Lakes Research, 32(4): 806-816.

Weimer, M., and M. Sowinski. 1999, J uly-August. Diet of the round goby (Neogobius

melanostomus) in Lake Erie. Dreissena! The Digest of National Aquatic Nuisance
Species Clearinghouse, 10: 7-12.

50

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