Florida's smalltooth sawfish mass die-off mystery deepens as lab results provide no clues

Experts in Florida are still struggling to understand why critically endangered smalltooth sawfish are swimming in circles and beaching themselves, despite testing hundreds of water samples and analyzing fish tissue. 

"The cause, or causes, of the abnormal behavior and mortality of fish in the Florida Keys (prominently including sawfish) remain unknown," Theresa Cody, associate research scientist at Florida Fish and Wildlife Conservation Commission (FWC) Fish and Wildlife Research Institute, told Live Science in an email. 

FWC has launched an intensive investigation, along with several partners, to understand what might be causing this strange behavior.

The Mysterious behavior has caused the deaths of at least 50 smalltooth sawfish (Pristis pectinata) and is also affecting other species.

Initial reports of smalltooth sawfish behaving in an unusual way began in fall 2023. The fish appeared to be acting erratically and spinning in circles. FWC started receiving reports of dead fish in January 2024 and believes the two might be related. Smalltooth sawfish were declared critically endangered in 2006, and it’s believed that 80% of populations have been lost in under 60 years, so every death could have a significant impact on the species’ survival.

The Florida Department of Environmental Protection (DEP) has tested the water for more than 250 different chemicals, but they revealed that none of the chemicals are at high enough levels to cause these deaths, according to a May 22 statement.

"We started with examining environmental conditions, water quality, water samples for Harmful Algal Blooms (HABs), and toxin analysis," Cody said. There is no indication that the die-off is down to red tide (Karenia brevis) algal blooms, according to tests so far — though investigations are still ongoing.