Scientists reveal why hundreds of fish in Florida Keys are spinning to death and washing up on popular beaches


Scientists may have discovered what has caused hundreds of fish off the coast of the Florida Keys to spin in circles until they die.

Reports of the bizarre behavior first surfaced in October 2023, leading to nearly 500 reports of dead fish washing ashore as of May 8.

Researchers at Florida Gulf Coast University recently analyzed more than 300 fish tissue samples and tested over 250 chemicals in the area to determine what could be causing this fatal fish spinning.

The team has now identified toxic algae on the sea floor in samples, which has suggested a bacteria emerged on the sea floor that is linked to neurological deficits including hyperactivity and twitching.

Researchers believe toxic algae growing on the sea floor could be causing hundreds of fish to have neurological issues
Researchers believe toxic algae growing on the sea floor could be causing hundreds of fish to have neurological issues

The Florida Fish and Wildlife Conservation Commission (FWC) and researchers found six dead smalltooth sawfish washed up on the shores of the Florida Keys last month, which are on the brink of extinction.

The sight, month with hundreds of reports, led to them opening an investigation.

The team sent the tissue samples to the University of South Alabama for toxin analyses, but reports showed there was no evidence of low oxygen levels, low salinity, pH, odd water temperature or red tide – a type of harmful algae bloom.

Although more studies need to be conducted to officially determine the root cause, the tests revealed natural toxins in both the seawater and the fish tissues, and elevated levels of the HAB, Gambierdiscus algae.

Gambierdiscus toxicus, loosely attached to algae on coral reefs and are then ingested by sea creatures.

‘The hypothesis I’m working on at the moment is really that the combination of these various benthic algal toxins are coming together to create the phenomenon we’re seeing,’ Alison Robertson, a senior marine scientist at the Dauphin Island Sea Lab, told NBC News.

Benthic algae live on the seabed off the shore, about 65 to 131 feet below the surface and can release toxins during algae bloom – when the algae population in the water rapidly increases.

Scientists still don’t know what caused the population to grow, but are now in a race against the clock to protect the smalltooth sawfish and other species from further exposure.

There have been more than 500 reports of spinning fish off the coast of Key West. The smalltooth sawfish is at the greatest risk because it is critically endangered, and already the phenomenon has claimed 47 lives
There have been more than 500 reports of spinning fish off the coast of Key West. The smalltooth sawfish is at the greatest risk because it is critically endangered, and already the phenomenon has claimed 47 lives
There have also been reports that smalltooth sawfish are beaching themselves, adding to the growing concerning behavior of other fish that have been seen spinning off the coast of the Florida Keys
There have also been reports that smalltooth sawfish are beaching themselves, adding to the growing concerning behavior of other fish that have been seen spinning off the coast of the Florida Keys

The cause has continued to baffle scientists who said when they removed the spinning fish from the seawater and placing them in a freshwater tank, some recovered in a span as short as 25 minutes.

Michael Parsons, a professor of marine science at Florida Gulf Coast University and an algae expert found the Gambierdiscus levels were four times higher than he’d ever seen or recorded before.

Last month, the FWC reported that Florida had seen an excess growth of toxic algae that can get into the mammal’s bloodstream through the food they eat, causing erratic swimming and death.

The algae have affected several fish species, but marine biologists are most concerned about the smalltooth sawfish, which has been classified as critically endangered since 2003.

The FWC reported that 47 sawfish have died, but it’s believed that number is much higher.

Researchers rescued a distressed smalltooth sawfish that was swimming in circles in Cudjoe Bay on April 5 and brought it to a temporary holding tank at the Mote Marine Laboratory in Sarasota, Florida.

The FWC and Mote hoped that by rehabilitating the smalltooth, they could better understand what caused the event, but when the animal continued to deteriorate, they decided to humanely euthanize the fish on May 2.

The smalltooth sawfish is a critically endangered species, believed to be due to habitat loss. The species once lived as far down as the coast of central west Africa up to North Carolina
The smalltooth sawfish is a critically endangered species, believed to be due to habitat loss. The species once lived as far down as the coast of central west Africa up to North Carolina
The FWC took blood and tissue samples from the rescued sawfish to determine if it had any toxins in its system
The FWC took blood and tissue samples from the rescued sawfish to determine if it had any toxins in its system

‘It was always our cautious hope to be able to utilize the best available science for the rehabilitation and release of the sawfish,’ said Dr. Michael P. Crosby, President & CEO of Mote Marine Laboratory & Aquarium.

‘Although heartbreaking, this outcome was not surprising,’ he said, adding: ‘We worked restlessly for 24 hours a day to provide the most advanced treatment available.

‘Sadly, even with our best efforts, the animal was ultimately too compromised to recover.’

The FWC is conducting a necropsy – animal autopsy – on the smalltooth and is sending samples to various labs for further analysis.

‘I honestly don’t think anything can reasonably be ruled out right now,’ Crosby told NBC.

As of May 6, more than 60 species were reported to have symptoms including the silver mullet, snook, bonefish, southern stingray, Atlantic sharpnose shark and spadefish, among others, according to Bonefish & Tarpon Trust, a marine conservation agency.

The organizations are asking the public for help identifying other deaths or abnormal behavior by calling the sawfish hotline: 844-4-SAWFISH.

This article by Nikki Main was first published by The Daily Mail on 13 May 2024. Lead Image: Tissue samples were sent to the University of South Alabama for toxin analyses, but reports showed there was no evidence of low oxygen levels, low salinity, pH, odd water temperature or red tide.

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