Evaluating short-term effects of omnivorous fish removal on water quality and zooplankton at a subtropical lake |
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Authors: | M J Catalano M S Allen M H Schaus D G Buck J R Beaver |
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Institution: | (1) School of Forest Resources and Conservation, Program for Fisheries and Aquatic Sciences, University of Florida, Gainesville, FL, USA;(2) Department of Biology, Virginia Wesleyan College, Norfolk/Virginia Beach, VA, USA;(3) School of Natural Resources and Environment, University of Florida, Gainesville, FL, USA;(4) BSA Environmental Services, Inc., Beachwood, OH, USA;(5) Quantitative Fisheries Center, Michigan State University, 153 Giltner Hall, East Lansing, MI 48824, USA |
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Abstract: | We evaluated a biomanipulation program to test for short-term changes in water quality (chlorophyll a, Secchi depth, total phosphorus) and macrozooplankton biomass following partial removal of omnivorous gizzard shad Dorosoma cepedianum. The removal occurred at a eutrophic subtropical lake, and responses were compared to an unmanipulated control lake using
a before-after-control-impact paired series analysis. The removal reduced the biomass of large (>300 mm) gizzard shad by 75%
over 2 years via a subsidized commercial gill net fishery. However, the total population biomass of gizzard shad was reduced
by approximately 32% from an average pre-manipulation biomass of 224 kg ha−1 due to the size selectivity of the gear, which did not effectively capture small fish (<300 mm). No significant short-term
changes in chlorophyll a concentration, Secchi depth, total phosphorus concentration or macrozooplankton biomass were detected following biomanipulation.
The partial removal may have fallen short of the biomass reduction required to cause ecosystem responses. Our results suggest
that moderate omnivore removals (i.e., <40% biomass reduction) will have little short-term benefits to these lakes, and future
manipulations should use a less size-selective gear to achieve a larger total biomass reduction. |
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