Clerkin, P. J. Nearshore fish community responses to changes in water clarity, Power Point Presentation, The 13th Annual Undergraduate Research Symposium: Experiences in Field Ecology, Department of Natural Resources, Cornell University, Ithaca, New York, December 2009.
Abstract: Reduced nutrient loading in New York’s Oneida Lake as a result of the Water Quality Acts of the 1970’s combine with the introduction of zebra mussels in 1991 have lead to increased water clarity over the last three decades, reversing the trend of eutrophication that has persisted since the early 19th century. We sought to understand how changing water conditions affected nearshore fish communities, and whether reversing eutrophic trends would result in reversed affects on nearshore fish observed in previous studies. We used a 75’ x 5’ beach seine with ¼ “ mesh to sample 9 long term sites. We used seine survey data from 1963-1970, 1976, 1978, 1989-1990, 2000, 2004, and 2007-2009 and categorized data collected prior to 1989 as eutrophic conditions and data collected after 1989 as post-eutrophic. We used this data to compare fish community trends under both eutrophic and post-eutrophic conditions to better understand nearshore responses to varying conditions of water clarity. We examine species richness of 45 fish species found in Oneida Lake (number of species before nutrient reductions), species-specific richness (number of species caught), and species-specific abundance (number of fish caught per seine hull). Study of species richness yielded no significant changes, decreasing from 23.77 species to 22.33 with a p-value of 0.29. Species-specific richness revealed significant increase in eight species while seven species showed a decrease and 28 species showed no significant change. These results agree with abundance analysis that shows seven species increasing significantly and 5species decreasing, while 33 species did not significantly change. These outcomes illustrate little change in species richness and abundance over different conditions of water clarity. Additionally, decreases in fish species attributed to eutrophication do not seem to be reverse after eutrophic conditions subside. These results point to the possibility that water clarity conditions could have less influence on lake communities than indicated by previous research.