JACKSONVILLE, Fla. – Biologists with the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute have determined that a fungus caused a fish kill in the St. Johns River in mid-October.
The FWC said it received reports of dead fish and fish with ulcers beginning Oct. 20. Reports came from an area of the river just south of Interstate 95 near Jacksonville and as far south as Green Cove Springs. The FWC said it responded by analyzing dead fish and water samples from the area.
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FWC biologists suspected that a fungus called "Aphanomyces invadans" caused an infection, which produced ulcer-like lesions and the eventual death of shad, mullet and menhaden in the St. Johns River. The National Oceanic and Atmospheric Administration confirmed the FWC's findings when it conducted specialized testing on diseased-fish samples provided by the FWC.
The fungus, which is a type of water mold, occurs naturally in estuaries and freshwater systems in Florida, generally in water bodies with lower salinity levels. Scientists have confirmed that it causes an ulcer-forming disease in estuarine and freshwater fish worldwide.
This is not the first time that fish with these types of ulcers have been seen in the St. Johns River. Reports of similar incidents date back to the late 1970s. However, biologists have no evidence that there is a connection between this fish kill and the large-scale fish kill that occurred in the river earlier this summer.