Endangered sawfish are again turning up dead in Florida waters, raising fears that a monthslong die-off that killed more than 50 last year could strike again.
As of Monday, six sawfish have died this winter among 22 reports of sawfish showing signs of distress and spinning in the water, a spokesperson for the Florida Fish and Wildlife Conservation Commission confirmed. Biologists were able to perform necropsies on five.
Two of the dead fish had been tagged when they were healthy to track movements. That included a 13-foot female discovered near Flamingo in Everglades National Park.
The sawfish had been tagged in 2023 by Florida State University researcher Dean Grubbs off Cedar Key, the farthest north a sawfish had been tagged, he said. At the time, scientists hoped that was a sign the species might be recovering after being nearly wiped out and added to the endangered species list in 2003.
This winter’s deaths come nearly nine months after the baffling kills that afflicted dozens of other species subsided.
Fifty-four sawfish deaths were confirmed last year, with hundreds more reported sick or dead, during a widespread die-off that lasted nearly six months. The ailing sawfish first showed up in the Lower Keys, a couple of months after anglers and boaters started spotting dozens of species exhibiting the odd, spinning behavior. Dead sawfish were eventually spotted miles away in the Upper Keys.
After months of quiet, a dead sawfish was spotted late December and a second on New Year’s Eve. The remaining four appeared this year.
Scientists suspect a toxic bottom-dwelling algae is making fish sick, although they are continuing to investigate what caused the algae to become lethal to sawfish.
The algae can produce cigua toxins, like the kind that produce ciguatera, and normally rests benignly on the seafloor or clings to seagrass. An event, possibly a scorching heat wave that swept across the Keys over summer 2023, may have changed the ecosystem’s dynamic in a way that allowed the algae to spread and become more damaging, scientists said.
Because sawfish spend much of their lives resting on the seafloor, and have gills located on their bottom, scientists suspect they are more susceptible.
Other fish species that showed signs of distress have been able to recover. Scientists at the University of South Alabama who examined hundreds of those species also found multiple toxins in their livers, making it hard to isolate the cigua toxin found in the sawfish as the cause
Some scientists suspect the two-monthlong heat wave, which caused widespread coral bleaching and made worse by rising temperatures fuled by climate change, triggered the event by changing the makeup and balance of power in the community of algae where sawfish live.
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