Monday, July 26, 2010

Fish Kills Can Happen in the Summer Too (Not Just Because of the Cold)

I'm sure everyone remembers this past colder than normal winter and all the fish kills that occurred. Warm water fish species such as snook and tilapia can't tolerate the extreme, prolonged cold that we saw earlier this year that resulted in the mass quantities of fish that died. But fish kills are also common this time of year too but this time it's due to the hot weather or extended periods of cloudy days. Hot weather during the summer months can cause fish kills because warm water doesn't hold as much oxygen as cold water so there's less oxygen for the fish. Also, if there hasn't been any rain for a long period of time (a condition we've seen this summer especially) then the water levels are lower overall which causes the water to heat up even more further depleting the oxygen. Fish kills can also occur when there are long periods of cloudy days. If there isn't enough sunlight for plants in the water to photosynthesize then they start using the dissolved oxygen in the water faster than they can produce it which lowers the oxygen. Most natural bodies of water are used to this fluctuation in the seasons but they can still occur. Florida Fish and Wildlife Conservation Commission (FWC) keeps track of fish kills in natural bodies of water (such as the hundreds of fish killed in the St. Johns River). If you see a fish kill in a natural lake or estuary you can report the location at or call the FWC Fish Kill Hotline at 800-636-0511.