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Cazenovia Lake Fish Kill Investigation (2010)

Survey Number: 710011

Survey Date: August 5, 2010

A number of largemouth bass with open red sores (hemorrhagic dermal lesions) were observed on Cazenovia Lake on 8/3/2010. A collection was made on 8/5/2010 of four largemouth bass with these lesions. The bass were actively feeding and were taken on crankbaits. They were iced and taken to Cornell University for analysis. On the day of the collection, a few dead bass were observed floating (5+/-). This didn't seem too alarming with the amount of catch and release bass fishing that goes on there. Over the next few weeks, we began to receive calls from anglers about bass with the lesions and dead fish being observed. Numbers of dead bass reportedly ranged from 10 to 100's. A Region 7 Aquatic Biologist was fishing the lake during this same time period and never noticed more than 15 in a single day of fishing. He was not actively looking for them though, just seeing them as he was fishing.

The results from Cornell University indicated that the bass had a higher than normal number of Dactylogyrus sp. on the gills. Dactylogyrus is a common parasite of wild freshwater fish. It's likely that a combination of an increased parasite population in the lake combined with an additional stress or other primary illness resulted in the higher number of parasites seen in these fish in 2010. High water temperatures may have been, and often is, the primary stress factor. No causative agent for the skin lesions could be determined. The bass tested negative for Viral Hemorrhagic Septicemia (VHS).

The incidence of red lesions declined in September, and bass with partially healed lesions or fully healed scars were were being caught . However, some population level decline may have occurred due to the summer mortality. Anglers were reporting slower than normal fishing during September, 2010.


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