Shad die-off is normal in winter

Tennessee Valley Authority (TVA)
Posted: 2/20/2009

If you’ve seen a lot of small dead fish floating on your reservoir this winter, don’t be alarmed. They are most likely threadfin or gizzard shad, and they are easily killed by cold water temperatures and rapidly changing weather.

Shad are an important baitfish in TVA-managed reservoirs, but—because shad are a prolific species and can repopulate quickly—fisheries biologists agree that die-offs have little impact on the overall fish population in most reservoirs. In fact, in smaller reservoirs, shad die-offs may be beneficial in controlling the shad population.

Shad are very sensitive to temperature and do not feed or move around much when temperatures fall below 50 degrees Fahrenheit. Die-offs typically occur when water temperatures drop to between 40-55 degrees, particularly when the change in temperature is quick and drastic. An arctic front with high winds may cool a shallow body of water by five degrees or more, increasing the potential for shad die-offs.

Die-offs also can occur in the spring when warm winds cause water temperatures to climb too quickly for shad to become acclimated.

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