Results from a Whole Lake Experiment: Response of Walleye and Yellow Perch Populations to Cormorant Management on Oneida Lake, NY

Oneida Lake provides a rare, detailed experiment chronicling the walleye and yellow perch population responses to the rise and fall of double-crested cormorant abundance from management actions.  In response to previous studies showing significant negative impacts of cormorant predation on percid populations in the lake, a gradient of cormorant management techniques were instituted in attempts to reduce sub-adult walleye and yellow perch mortality and rebuild the adult percid populations.  Here we provide the results from these management actions and evaluate the effectiveness of the actions to increase recruitment into the percid fishery. Adult percid abundances did increase with the institution of cormorant management.  Percid sub-adult mortality decreased with intense, year-round cormorant management.  Consumption of percids decreased, however changes in the fish community also occurred which influenced cormorant foraging. Considerations also need to be taken regarding the timing of the percid recovery in Oneida Lake since adult percid abundance increased without the expected lag-time. Overall, cormorant management to improve fishery demographics was effective on Oneida Lake; however the clearest responses were during years with year-round management which is costly to maintain and has not been done on Oneida Lake since 2009.