Florida Keys Abnormal Fish Behavior Event Fall 2023 - Present

Spinning Fish Update

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• Dissolved oxygen, salinity, pH, and temperature are not suspected to be the cause of the fish behavior or kills.
• The Florida Department of Environmental Protection conducted water testing for more than 250 chemicals within the area of interest. Most chemicals were below detectable limits, and none were present at biologically significant concentrations. Sediment sampling showed no elevated concentrations of heavy metals. Laboratory results are available on the Watershed Information Network (watch this video first for a tutorial on accessing data).
  • This effort includes long-term sites that are sampled at least quarterly by either DEP or Florida International University: G5AP0015, South Cudjoe Key Ocean Side (24.632, -81.500);, G5AP0016 - Sugarloaf Key Bay Side (24.679, -81.571); G5AP0017 - Shark Key Bay Side (24.606, -81.654); G5AP0026, Coupon Bight (24.651, -81.366); 506-W, Little Torch (24.659, -81.383); 314-W, Bluefish Channel (24.718, -81.428).
  • Also included were targeted sites where the highest number of abnormal fish behavior reports were received, with exact locations lined up with historically data: LB41, North Little Torch Key Bay Side (24.718, -81.428); LB44, Johnson Key Back Country (24.711, -81.578); 42-POINT E, Canal Little Torch Key Grid offshore corner (24.677, -81.382).
• Necropsy data to date continues to show no apparent signs of a communicable pathogen (e.g. parasites, bacteria, viruses) that could have caused the spinning behavior and mortality.
• Microbiome analysis of sawfish and teleosts (bony fishes) was conducted using samples that included brain, spinal fluid, or blood. The results were negative for any known pathogenic viruses. The identified sequences were either from the host or bacteria (normal flora or environmental contaminants). No consistent patterns were found between species, including Gray Snapper, Silver Mullet, and Goliath Grouper.
• Preliminary histological examination revealed some similar potentially informative lesions in the brain tissues of teleosts (bony fishes) and sawfish, but the investigation is ongoing.
• Testing of water, benthic algae, and fish tissue has not detected red tide toxins (brevetoxins produced by Karenia brevis), cyanobacterial toxins, or saxitoxins as potential causes.
• Other harmful algal species were observed in benthic and water samples examined by FWC and Florida Gulf Coast University (FGCU).
• Elevated levels of the potentially harmful algae, Gambierdiscus spp., were observed in water and benthic samples early in the response by both FWC and FGCU. In March 2024, lower cell concentrations were observed in water samples followed by no observation of Gambierdiscus spp. in May and June’s water samples. FGCU reported lower cell numbers in benthic samples from the June sampling efforts. These observations were in line with cell concentrations measured in pre-event sampling from Monroe County. With the warmer, summer water temperatures, a reduction in Gambierdiscus spp. abundance was observed.
• FWC and partners sent >300 fish tissue samples, including sawfish, to University of South Alabama (USA)/Dauphin Island Sea Lab (DISL) for toxin analysis. Associated toxins were detected in water and benthic samples as well as fish tissues by USA/DISL. Work is ongoing to determine if this is the cause of the unusual behavior.
• In March 2024, the Lower Keys Guides Association reported pelicans behaving abnormally to the FWC. Of the four pelicans collected, no clinically significant lesions were noted during gross or histological examination, except for some evidence of myocarditis (inflammation in the heart) in one case. Heavy metal testing did not reveal any clinically significant levels of heavy metals. Tissues have been sent to USA/DISL for further toxin analysis. 

Sawfish Update

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• FWC sent 40 smalltooth sawfish tissue samples as well as sawfish blood samples (including pre-event samples) to the University of South Alabama for toxin analysis.
• Working with NOAA Fisheries, the FWC participated in the attempt to rescue and rehabilitate an 11-foot male smalltooth sawfish from Cudjoe Key on April 5, 2024. The animal was held at Mote Marine Laboratory’s facilities for rehabilitation but unfortunately, never recovered and was eventually euthanized on May 2. Additional participants in this rescue included: Ripley’s Aquariums, Mote Marine Laboratory, and Dynasty Marine Associates, Inc. (Additional information on deceased rescued sawfish) FWC staff have conducted necropsies on recovered smalltooth sawfish, blood and tissue samples are currently under analysis.
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The Florida Fish and Wildlife Conservation Commission (FWC) continues to document and investigate the cause of abnormal fish behavior (spinning) and small-scale fish mortalities in the Keys. Smalltooth sawfish are among the species observed exhibiting abnormal swimming behavior and sometimes dying. Although reports of fish exhibiting spinning behavior declined over the summer, the investigation continues through the collection and analyses of water and/or tissue samples. No sawfish have been reported to be spinning or dead related to this event since August 14th. 

The FWC continues to work collaboratively with the Florida Department of Environmental Protection (DEP), Florida Gulf Coast University, University of South Alabama, Bonefish & Tarpon Trust, University of North Carolina at Wilmington, and the Lower Keys Guides Association as well as other federal, state, local agencies, non-government organizations, stakeholders, and the community.

While the exact cause, or causes, of the spinning behavior and sawfish mortality in the Florida Keys remains unknown, FWC and its partners continue to investigate the potential role of Harmful Algal Bloom (HABs) species, given that several endemic HAB species (including Gambierdiscus spp., Protoceratium reticulatum, Pyrodinium bahamense, Coolia sp., Ostreopsis sp., multiple Prorocentrum species, and Pseudo-nitzschia spp.) were identified in water and benthic samples. USA/DISL detected HAB associated algal toxins in both water and fish tissues. More work is needed to determine whether one or more of these species and toxins are the cause of the unusual behavior.  

Public reports are an essential resource for our investigation into this event.