Updates

Since December 2024, FWC received 44 reports of fish spinning behavior (over 500 related reports since December 2023), to the Fish Kill Hotline, including many relayed in 2024 by Bonefish & Tarpon Trust and the Lower Keys Guide Association, and these reports have been critical for guiding research and response efforts. Affected fish have been observed through much of southern Monroe County, but primarily in the Middle and Lower Keys.  

Since December 2024, FWC received 22 reports of sawfish behaving abnormally in the greater Keys area that are potentially related to the spinning event (over 200 reports received since December 2023), to the Sawfish Hotline. During this time, there have been six sawfish mortalities and five of those have been necropsied (62 total mortalities since December 2023).

The Florida Legislature allocated $2 million to support this investigation. From this funding, Bonefish & Tarpon Trust received $1.75 million of this allocation to research the scope and scale of the event in Biscayne Bay, Florida Bay, and the Florida Keys during the 2024-2025 state fiscal year. This funding supports data collection and analysis while also employing local fishing guides to assist with the sampling efforts. 

What We Know So Far: 

• Water Quality: The Florida Department of Environmental Protection (DEP) tested the water for over 250 chemicals in 2024. None were found at harmful levels. Sediment tests also showed no concerning levels of heavy metals. Sampling in 2025 will target spinning “hotspots” as identified by the investigation team; hotspots have not yet been observed in 2025.  

• Fish Health: No signs of parasites, bacteria, or viruses that could explain the unusual fish behavior have been found. Scientists did find some subtle changes in the brain tissue of affected fish, but more research is needed. Additional fish collections by FWC occurred in December 2024 and February 2025.  

• Algae & Toxins: No red tide or other common harmful algal toxins were found in 2024, although a bloom of the red tide alga Karenia brevis was observed in the Keys in January and February of 2025 resulting in concurrent fish kills. Testing of water, benthic algae, and fish tissue has not implicated red tide toxins (brevetoxins produced by Karenia brevis), cyanobacterial toxins, or saxitoxins as potential causes of the spinning and sawfish mortality event in 2024.  A type of microalgae called Gambierdiscus spp. was present at elevated levels in winter and spring of 2024 but has since decreased. Scientists have found a number of algal toxins in fish tissues, and these are currently being investigated as potential causes, either independently or in combination with each other.