Comparison of Micropterus salmoides population characteristics between two
basins Onondaga Lake, New York
Photo Credit: Onondaga County Department of Water Environment Protection
Danielle Hurley
M.S. Candidate Fisheries Biology and Management
SUNY College of Environmental Science and Forestry
Final Report
Edna Bailey Sussman Foundation
December 2013
Introduction
Onondaga Lake, NY has a long history of industrial and municipal pollution. It was once
considered the most polluted lake in the country (Effler 1996). Facility upgrades at the Syracuse
Metropolitan Wastewater Treatment Plant, discontinued industrial waste disposal into the lake,
and the colonization of zebra mussels have led to increased water clarity and macrophyte
abundance and diversity (Kirby 2009). Currently, Honeywell International is carrying out a
$450 million remediation project that includes the dredging and the capping of contaminated
sediments. The majority of these sediments are located in the southern basin of the lake.
Following the removal of contaminated sediments, Honeywell International will restore habitat
in these areas. This should be beneficial to a variety of fish and wildlife that utilize Onondaga
Lake as well as increase recreational opportunities.
Improvements in water quality in the past few decades have resulted in the development
of a diverse warm water fish community. Sixty five species of fish have been documented in the
lake in recent years and in annual surveys it is typical to capture between 30 and 40 different
species. Catch and release Largemouth Bass fishing has become very popular on Onondaga
Lake. In 2007 a Bass Masters tournament was held on the lake with a $250,000 grand prize.
Although the fishery has greatly improved and gained popularity, past ESF data have shown that
the Largemouth Bass fishery has been highly variable, but that electrofishing catch rates are
consistently higher in the northern basin than the southern basin. My study has begun to
investigate if there are dissimilarities in the Largemouth Bass population structures that may be
due to habitat differences in the North and South basins. Understanding these differences may
predict how the Largemouth Bass population will respond to future habitat remediation.
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Methods
Population Estimate
Between May and July 2013 Largemouth Bass were sampled throughout Onondaga Lake
during mark recapture events. The shoreline was sampled four times at 1-meter depth using a
5.49 m Smith Root electrofishing boat. I used 170 V pulsed DC at 120 Hz and generated 2025A. During the first three sampling events all Largemouth Bass larger than 200 mm received a
fin clip and all Largemouth Bass 300 mm or larger had a numbered tag implanted. During
events 2 through 4 all Largemouth Bass were inspected for fin clips and tags. I was unable to
sample a portion of the southern basin due to dredging activities. Electrofishing was performed
between sunset and sunrise. Population estimates were made for the entire lake, as well has for
each basin individually, using the Schnabel estimator (Hayes et al. 2007):
̂=
𝑁
∑𝑡𝑖=2 𝑛𝑖 𝑀𝑖
∑𝑡𝑖=2 𝑚𝑖 + 1
where t is the number of sampling events, ni is the number of fish captured during the ith event,
mi is the number of fish recaptured in the ith event and Mi is the number of already marked fish
in the population during the ith event.
Age and Growth
Scales were collected during the mark recapture sampling to estimate Largemouth Bass
ages. An attempt was made to collect 10 scale samples per 25 mm size class (0 mm-550 mm)
per basin. This was achievable for most size classes. Fewer scales samples were collected from
the very small and very large bass. Scales were pressed onto cellulose acetate slides and aged by
projecting the slide on a microfiche projector and counting the apparent annuli. Measurements
were made between each annulus to back calculate length at age using the Fraser-Lee Equation
(Isely and Grabowski 2007):
𝐿𝑖 =
𝐿𝑐 − 𝑎
𝑆𝑖 + 𝑎
𝑆𝑐
where Si is the radius at annulus formation, Sc is the overall radius of the scale, Li is the length at
annulus formation, Lc is the fish length at time of capture, and a is the length at time of scale
formation.
Diet
Stomach flushing using a syringe was used to collect stomach contents from Largemouth
Bass in late July and early August. Contents were fixed in 10% buffered formalin and then
identified at a later date. An attempt was made to sample 30 fish per basin that contained
stomach contents. The Frequency of Occurrence Index (Chipps and Garvey 2007) was used to
determine if Largemouth Bass in each basin utilize similar or different prey resources.
Frequency of occurrence is calculated using the following equation (Chipps and Garvey 2007):
𝑂𝑖 =
𝐽𝑖
𝑃
2
where Oi is the frequency of occurrence value, Ji is the number of fish containing prey item i, and
P is the number of fish that contained stomach contents.
Eleven Largemouth Bass were sacrificed to validate that the stomach flushing technique
was successful. These fish first had their stomachs flushed. They were then killed and their
digestive tracts were dissected to uncover any remaining content.
Preliminary Results
Population estimate
A total 1977 Largemouth Bass were sampled throughout Onondaga Lake during the mark
recapture events. In the north basin 1140 Largemouth Bass were sampled and in the south basin
837 were sampled. Of the total captured bass, 1733 were above 200 mm and included in the
population estimate. The whole lake was estimated to have a population of 13078 Largemouth
Bass 200 mm or larger with a confidence interval of 10739-16718. The north basin was
estimated to have 8206 (6301-11763) Largemouth Bass 200 mm or larger and the south basin
was estimated to have 5544 (4220-8081) Largemouth Bass 200 mm or larger, where the values
in parentheses represent confidence intervals.
Table 1. Population estimates for Largemouth Bass for the whole lake and each basin individually using the
Schnabel estimator Onondaga Lake, New York 2013. Separate estimates were made for bass over 200 mm and bass
over 300 mm. Largemouth bass are legal catch size at 305 mm. Confidence intervals appear in parentheses.
Largemouth Bass Population Estimates (Confidence Intervals)
Size Range
Whole lake
North
South
≥200 mm
13078 (10739-16718)
8206 (6301-11763)
5545 (4220-8081)
≥300 mm
3819 (2858-5751)
3132 (2057-6557)
1171 (814-2084)
Age and Growth
I have been able to age 143 scale samples from the north basin and 65 scale samples from
the south basin. Back calculation of growth has shown that most Largemouth Bass in Onondaga
Lake enter the legal fishery (305 mm) in either their fourth or fifth growing seasons.
Comparisons in growth will be made between basins when aging of scale samples from the south
basin has been completed. Scales taken from recaptured Largemouth Bass that were captured in
previous years will be used to validate age estimates.
Diet
Stomach flushing (modified from Meehan and Miller 1778) was performed on 137
Largemouth Bass throughout the whole lake. A total of 58 Largemouth Bass had contents in
their stomachs. In the north basin 30 Largemouth Bass were sampled with contents in their
stomachs and 23 were sampled with empty stomachs. Twenty eight Largemouth Bass contained
stomach contents in the south basin, while 44 had empty stomachs. To date 19 stomach samples
have been processed from each basin. The frequency of occurrence index suggests that Round
Gobies are the most common food resource for Largemouth Bass in Onondaga Lake, followed
by Banded Killifish. Although Round Gobies were the most frequently found prey item in both
the north and south basins the frequency of occurrence values were very different. Round gobies
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were found more frequently in Largemouth Bass stomachs in the north (0.79) than in the south
(0.37).
Table 2. Frequency of Occurrence values for prey items found in Largemouth Bass stomachs in the north and
south basins of Onondaga Lake 2013.
Frequency of Occurrence Values for Each Prey
Item
Species
North
South
Round Goby
0.789
0.38
Banded Killifish
0.105
0.158
Alewife
0.051
0
Lepomis
0
0.053
Largemouth Bass
0
0.053
Unidentified Fish Matter
0.632
0.684
Zebra Mussels
0.053
0.211
Tadpole Madtom
0.053
0.053
0
0.053
White Perch
Discussion
Based on Schnabel estimates, Largemouth Bass are more abundant in the north basin than
in the south basin. Largemouth Bass are known to be generalist predators. Bass in both basins
showed a fairly diverse diet. Round Gobies appear to be a more common food resource in the
north basin than in the south basin. This may be due to the distribution of Round Gobies
throughout the lake. Through personal observation there seems to be a higher density of Round
Gobies in the north basin. My preliminary evaluation of the Largemouth Bass populations
suggested that there is little difference in population characteristics between basins, but there is a
larger population of bass in the northern basin. This may be due to more favorable habitat and
greater numbers of prey items. Largemouth Bass from the south basin may also have moved into
the north basin to avoid large dredging areas currently present in the southern basin.
Future Research
I will continue to age Largemouth Bass scales samples and compare growth rates
between the two basins. The remaining diet samples will be processed and the frequency of
occurrence index will be updated to include the remaining data. I also plan to utilize fin rays,
otoliths, and cleithrum from Largemouth Bass to estimate ages. This will be used to determine
the most accurate and appropriate method for estimating age of Largemouth Bass in Onondaga
Lake for the future. Length and weight data will be further analyzed to enhance the comparisons
of the north and south basin Largemouth Bass populations.
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Acknowledgements
I would like to thank the Edna Bailey Sussman Foundation for their financial support and
the guidance of Emily Zollweg-Horan from the NYSDEC, which made this work possible. I am
extremely appreciative of the guidance and support of my major professor Dr. Neil Ringler.
Also, I am very grateful to all of those who helped me in my data collection including Zachary
Smith, Anne Burnham, Kyle Hodgson, Dan Anderson, Harold Nugent, Rachael DeWitt, and
Stephanie Johnson. Thank you also to Lucus Kirby, Stephanie Johnson, Matthew Gunderson,
Curtis Karboski, and Stephan Tyszko who provided much guidance in the planning of this
project.
References
Chipps, S.R. and J.E. Garvey. 2007. Assessment of Diets and Feeding Patterns. Pages 473-514
in C.S. Guy and M.L. Brown, editors. Analysis and Interpretation of Freshwater
Fisheries Data. American Fisheries Society. Bathesda, Maryland.
Effler, S.W. and G. Harnett. 1996. Background. Pages 1-29 in S.W. Effler, editor.
Limnological and Engineering Analysis of a Polluted Urban Lake: Prelude to
environmental management of Onondaga Lake, New York. Springer-Verlag New York,
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Isely, J.J. and T.B. Grabowski. 2007. Age and Growth. Pages 187-228 in C.S. Guy and M.L.
Brown, editors. Analysis and Interpretation of Freshwater Fisheries Data. American
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Onondaga Lake, New York. MS thesis. State University of New York, College
of Environmental Science and Forestry. 78 pp.
Meehan, W. R., and R. A. Miller. Stomach flushing: effectiveness and influence on survival and
condition of juvenile salmonids. J. Fish. Res. Board Can., 35: 1359–1363 (1978).
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