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Scientists continue to search for what's poisoning Lower Keys fish. Another dead sawfish is confirmed

A sawfish in shallow water near South Florida
Jamie Mae Darrow
Florida Fish and Wildlife Research Institute
Since Jan. 30, nearly 50 sick or dying sawfish have been reported to state wildlife officers who have collected samples from 16.

The number of sightings of sick sawfish in the Lower Keys has increased to 49, with 16 deaths confirmed, Florida wildlife officials said Friday.

That increase comes amid a mysterious outbreak of unusual fish behavior spotted mostly between Bahia Honda and Sugarloaf Key starting in November, when struggling fish appeared spinning, fighting to stay upright or poking their heads out of the water. Two months later, the sick and dead sawfish started washing up on flats and beaches.

Species have included tarpon, snook, permit and other large fish, as well as grouper, snapper and small baitfish.

READ MORE: Number of dead, dying sawfish in Lower Keys continue to mount

It’s not yet clear what’s ailing the endangered fish, which was added to the Endangered Species List in 2003 after nearly disappearing. The outbreak comes on the heels of an unprecedented ocean heat wave that drove temperatures in some nearshore spots to over 100 degrees. Coral throughout the Keys and parts of Miami-Dade bleached.

But usual hazards that trigger fish kills, including low oxygen from high temperatures, red tide or high salinity, have been ruled out. And ongoing work to isolate a toxin in sick fish collected from the area has failed to narrow the culprit.

“There’s something toxic. We don’t know what, though. It could be anything,” said Mike Parsons, an algae expert at Florida Gulf Coast University working with the University of South Alabama to identify the toxin. “We were kind of hoping that there would be a stronger signal that we could easily see, but it's just as messy as everything else that we get.”

Scientists initially focused on a tiny toxin found in ciguatera, after water samples revealed elevated levels of the gambierdiscus dinoflagellate. But lab tests that involved isolating the toxin and growing it in lab cultures instead revealed multiple toxins.

“All we know is that we had cell death, but we don’t know what caused it,” Parsons said.

Work on the toxin is also relatively new. The toxin produced by gambierdiscus in ciguatera was only identified last year, he said. It can also appear in multiple forms, depending on where it’s found, which can making looking for it like finding a needle in a haystack.

“There is a whole lot of new science that goes into that,” he said.

Water testing by the Florida Department of Environmental Protection has also ruled out the presence of pesticides or herbicides that might poison fish, he said. In addition to toxins, investigators are looking for clues that would tell them whether the toxin is related to the water or what fish are consuming.

Meanwhile, concern is growing among people who work on the water and normally used to seeing seasonal fish kills.

The Lower Keys Guides Association is asking for public help and created a link for reporting unusual behavior at LKGA.org. They also posted links for reporting unusual behavior, including hotlines with the Florida Fish and Wildlife Conservation Commission and state wildlife research institute. To specifically report sawfish, call 1-844-4SAWFISH.

Members of the guides association, who first reported the sick fish, are working with Bonefish Tarpon Trust to collect samples. The two groups also recruited state and university experts to form a working group and coordinate the investigation, according to the LKGA. This week, at least five boats were on the water sampling water where sick fish were spotted.

It's also not clear that scientists are finding all the dead sawfish, since they've only been found on the Atlantic side of the islands, where there are fewer mangroves.

"Whether it's going on 15, 17 or 19 is not particularly relevant," said Tom Matthews, manager of the Florida Fish and Wildlife Research Institute's Marathon lab. "Deaths of sawfish are still occurring. It's unlikely we'll find all of these."

Later this month, Parsons said they will begin testing water where no sick fish have been spotted to look for differences. They also want to better define the boundaries of where sick fish are being found, which could shed light on how currents or tides may be affecting the event.

“Hopefully we can figure it out and then once we do, how long's it going to last?” he said. “Hopefully it'll go away. Will it go away for good? Is this a one in 1,000,000 shot? Who knows?”

Jenny Staletovich is WLRN's Environment Editor. She has been a journalist working in Florida for nearly 20 years. Contact Jenny at jstaletovich@wlrnnews.org
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