ST. PETERSBURG, Fla. — A mysterious affliction that causes prehistoric, endangered smalltooth sawfish to spin erratically in Florida waters and often die appears to have resurfaced, with more than 50 deaths recorded last year, wildlife officials said Wednesday.
Following a roughly nine-month lull, there have been 22 reports of the odd spinning behavior involving sawfish in waters around the Florida Keys since December, the state Fish and Wildlife Conservation Commission reported. Six sawfish deaths were reported in this recent outbreak.
It’s unclear what is causing the problem that led to at least 54 sawfish deaths last year. The agency reported that testing for parasites, bacteria, viruses and more than 250 chemicals, as well as checks for such issues as toxic red tide, turned up nothing definitive.
“Scientists did find some subtle changes in the brain tissue of affected fish, but more research is needed,” the agency said in a statement.
Sawfish, related to rays, skates and sharks, are named for their elongated, flat snout that contains a row of teeth on each side. Sawfish have been around for millions of years, can live for decades and grow quite large, with some as long as 17 feet (about 5 meters). They were once abundant off the coast of the southeastern U.S. but now are mainly located off the coast of southwestern Florida and the Keys island chain, as their habitats shrink.
Since December 2023, more than 500 reports of spinning sawfish and other species have been documented.
After the initial deaths, state legislators approved $2 million to fund the investigation into sawfish deaths in Biscayne Bay near Miami, Florida Bay and the Florida Keys. Some of the money goes to local fishing guides for water sampling and other work, according to FWC. There is also a sawfish hotline for people to report spinning or whirling fish.
One theory is that a lengthy heat wave last year largely attributed to climate change and blamed for bleaching corals may have changed the algae in ocean waters, especially near the sea floor, where sawfish are often found. Like rays, sawfish gills are on their undersides, so their intake is frequently from the bottom.
“Scientists have found a number of algal toxins in fish tissues, and these are currently being investigated as potential causes,” the FWC said.
The smalltooth sawfish has been on the U.S. endangered species list since 2003. Florida prohibits intentionally capturing, harming or harassing sawfish.
In recent years, threatened manatees also suffered a major die-off in Florida waters as pollution killed much of their seagrass food source. State and federal officials fed tons of lettuce to manatees that gathered in winter outside a power plant for two years, and the manatee numbers have rebounded somewhat, with 565 deaths recorded in 2024 compared to a record 1,100 in 2021.