The recent rains and cloudy skies are causing more than just flooding problems along the St. Johns River and other rivers and lakes in Central Florida. Residents have been reporting fish kills in various areas, and fisheries biologists with the Florida Fish and Wildlife Conservation Commission (FWC) think the number and severity of fish kills will increase over the next several weeks.

“We have already seen minor fish kills resulting from low dissolved oxygen (DO) levels in the St. Johns River, the Withlacoochee River and several lakes, but conditions are prime for a major kill,” said Marty Hale, regional biological administrator for the FWC’s Division of Freshwater Fisheries in Ocala.

What do heavy rains and cloudy skies have to do with fish dying from a lack of oxygen?

“The heavy rains wash organic debris, such as plant and animal material, into the waterways and stir up the bottom sediments. As the debris decays, this process uses the dissolved oxygen in the water faster than it can be replenished. At the same time, the overcast skies and muddy waters reduce sunlight so algae does not produce oxygen, and the result is that there is not enough dissolved oxygen in the water for the fish to breathe.

“That is when fish begin coming to the surface and gulping air. Ultimately the fish die and float to the surface,” Hale said. “The size of the fish kills depends on how low and widespread the DO levels are. They can range from only a few individuals being affected to massive kills where millions of fish die.”

Many different species of fish have been affected by the current fish kills, including largemouth bass, bluegill, black crappie and catfish.

Please report fish kills to the FWC Fish Kill Hotline at 1-800-636-0511, the FWC Ocala office at 352-732-1225 or the Department of Environmental Protection in Orlando at 407-894-7555. For questions regarding the safety of consuming distressed or dying fish call your local health department.