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Cold Water and Fish Kills Along Florida’s East Coast

The Fish and Wildlife Health Group and researchers at the Tequesta Field Lab are investigating a possible cold-water event.

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Florida Fish and Wildlife Conservation Commission's (FWC) Fish and Wildlife Research Institute (FWRI) scientists in St. Petersburg and at the FWC Field Lab in Tequesta have been following a widespread cold-water event off the east coast. Reports of cold water and poor offshore fishing have been noted in newspaper fishing columns and online fishing forums from Palm Beach to Jacksonville for four to six weeks, but mortality reports are concentrated in the Palm Beach and Martin County areas.

A fish mortality event was reported to the FWC Fish and Wildlife Health Group Thursday, July 3, 2003. An observer from the Juno Beach area reported floating, dead, and moribund adult reef fish species along the beach; the species included porkfish, snappers, grunts, cowfish, trumpetfish, angelfish, and filefish. The fish had distended abdomens; moribund fish had difficulty maintaining equilibrium and could not swim down into the water. Surface water temperatures along the beach were 10°–15° C range. Researchers collected and examined water and two adult porkfish. No harmful algal bloom species were noted in the water samples; results of biotoxin analysis were negative. The porkfish appeared normal—except both had distended abdomens, and one fish had a ruptured swim bladder.

The east coast cold-water upwelling has occurred in the past and affected fishing (1984, 1988, 1994, 1996, and 1998 from several as yet unconfirmed sources), but anglers and FWC staff report this years' upwelling is stronger (colder) and more persistent. The likely cause of the July 3 fish kill was that the fish were "caught" in an upwelling current, and as they rose in the water column, their swim bladders quickly inflated and ruptured in some cases. This affected their ability to maintain proper buoyancy and equilibrium. A similar result often occurs when reef or bottom dwelling fish are caught on a hook and reeled quickly to the surface.

On July 21, 2003, a resident and avid diver from West Palm Beach reported dead and dying fish lying on the bottom near Miss Jennie, a wreck site. The report also noted that water temperatures were very cold. The fish that were still alive appeared stunned, probably an effect of the cold water. Affected species reported were similar to the Juno Beach mortality event. Also on July 21, 2003, a diver reported multiple reef fish species lying dead on the bottom on the reefs just north of the St. Lucie Inlet.

On July 22, 2003, FWC staff members diving in the Jupiter Inlet area observed millions of stunned and dead fish and invertebrates of all sizes and many species. Many usually hidden creatures were in the open; for example, stunned morays were found on the bottom, fully exposed. The bottom water temperature was recorded at 14°– 15° C and the surface at 26° C. Researchers reported seeing a large school of vermilion snapper at a reef at a depth of 18 ft. Normally, vermilion snapper are found in 100 ft+ deep water, but these were apparently searching for a warm water refuge. Corals also appeared to be affected. A report from the "Hole in the Wall" dive site off Palm Beach County noted a bottom temperature of 12.8° C. Additional water and fish samples will be collected and tested for biotoxins to determine their involvement, if any. No dead fish were observed on the surface, and no reports of dead fish along the beaches have been received.

Please report any observations of moribund or dead fish or invertebrates to FWC’s Fish Kill Hotline at 1-800-636-0511, or report your observations online:
http://research.myfwc.com/fishkill/submit.asp