Dead floating fish foul ponds with warm-up

The problem could last months

By Mark Collins - Meteorologist

Bloated fish killed during the January cold have resurfaced weeks later with the warm-up in this St. Johns county pond.

JACKSONVILLE, Fla. - Dead fish that sank to the bottom during January's cold are floating to the top of of freshwater ponds with the return to warmer temperatures,

January was hard on fish that couldn't find warmer deep water pockets. Many died during the prolonged 20 days of below average January days and 12 freezes in Jacksonville.

Many of the fish that sank to the bottom are starting to float to the surface weeks later. 

Warmer more buoyant water along with gasses from the carrion, or decomposing animal flesh, are floating the smelly carcasses.

The smell could last over a month unless the carcasses are physically removed.

A study of Perch in German lakes found complete decomposition can take up to 70 days and 25 days for half the fish to rot away.

It takes 25 days for a Perch to decompose 50% close to shore in a freshwater lake and 70 days to disappear completely.

Winter algal productivity can also kill fish by reducing oxygen in the water. University of North Florida Biologist Dr. Kelly J. Smith said this recent kill was cold related.  UNF monitors two freshwater areas and did not observe unusual low dissolved oxygen levels in any samples 

Dr. Kelly said she saw a large number of catfish that floated to the surface, but due to cold, since we had water temperatures dropping to 10C. 

Also she mentioned, most water bodies in this area are continually mixed by the winds in the winter, so there is no stratification of bottom waters to cause poorly oxygenated water.


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