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For Release: Friday, April 5, 2013

DEC: Cold Temperature Stress in Late Winter Causes Cyclical Fish Die-Off in Local Waterbodies

Large numbers of dead and dying fish have been observed in area waters including Lake Erie, Buffalo Harbor, upper and lower Niagara River and Niagara County waters of Lake Ontario, the New York State Department of Environmental Conservation (DEC) reported today. Dead and dying fish have also been observed along the Pennsylvania and Province of Ontario shorelines of Lake Erie and along the Ontario shoreline of the Niagara River. Inspections by DEC Aquatic Biologists in the Buffalo Harbor and Upper Niagara River indicate that nearly all of the dead and dying fish observed are gizzard shad, a medium-sized member of the herring family.

"Mortality of gizzard shad in late winter and early spring is common and occurs cyclically, although it usually affects lower numbers of shad locally," said Regional Fisheries Manager Mike Clancy. "This species is very sensitive to cold water temperatures and their inability to acclimate causes mortality at low temperatures."

Gizzard shad are living near the northern edge of their range in the Great Lakes, making them especially susceptible to cold temperatures. DEC's Lake Erie netting survey in autumn 2012 found gizzard shad numbers to be the highest observed in the last seven years. Generally mild winters may have allowed their population to increase during recent years.

Because the gizzard shad mortality is widespread and primarily affects one species of fish, their die-off is not considered an indicator of an environmental problem such as pollution. Mortality of a single species of fish suggests that the die-off is the result of a disease, parasite or species-specific stressor. In this particular case, late winter cold stress is the suspected cause.

DEC has collected and submitted a sample of gizzard shad to Cornell University's pathology laboratory for disease screening. Additional information about gizzard shad, including images, is available on DEC's website.

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