Wednesday, June 5, 2024

Florida Fish "Spinning Disease" Remains a Mystery

In late 2023, researchers began documenting abnormal fish behavior in the Lower Florida Keys (USA), with over 50 species observed spinning and swimming upside-down. Following unprecedented mortalities of endangered smalltooth sawfish (Pristis pectinata), in March 2024 NOAA Fisheries announced a first-ever plan to attempt to rescue, rehabilitate, and release affected sawfish. In April 2024 an 11-foot male sawfish was rescued from the Keys and transported to the mainland for rehabilitation, but after almost a month of veterinary care the sawfish succumbed to the mystery illness and had to be euthanized. Over 200 reports of affected sawfish have been received, with 50 recovered mortalities. Necropsies were performed on most recovered sawfish with numerous samples and tissues collected for further analysis. Necropsies showed no apparent signs of a communicable pathogen or bacterial infection. Results of water testing from the area indicated dissolved oxygen, salinity, pH, and temperature were not suspected to be the cause of the fish behavior or kills. Similarly, water testing found that more than 250 chemicals were either not detected or were below any biological thresholds. Water and benthic samples tested for microalgae found red tide (Karenia brevis) was not present, but Gambierdiscus spp. dinoflagellates and their associated ciguatera toxins were. Ciguatoxins were also observed in some fish tissues, but more research is needed to determine if this is the cause of the unusual behavior and deaths. With the height of the emergency event appearing to now be over, the U.S. Smalltooth Sawfish Recovery Implementation Team is currently working with numerous partners at aquariums, universities, state and federal agencies, and non-profit organizations to determine the cause of the sawfish mortalities and plan for future similar events by developing the infrastructure for a permanent sawfish rescue and rehabilitation program. I'll keep you updated as our test results come in and we learn more.

To stay up to date on all the latest research and findings visit FWC's Florida Keys Abnormal Fish Behavior Event page at