In the mystery of Florida’s strange spinning fish, a great suspicion has arisen

A mysterious illness in a fish in the Florida Keys has sent it spinning in circles after a frantic race to find the cause and save an endangered species before it’s too late.

Eight months into the scientists’ hunt, some think a prime suspect has emerged: Toxins from algae colonizing the sea floor may be causing neurological problems in some fish species.

Fishermen noticed the strange behavior in October, according to Ross Boucek, a fisheries ecologist with the Bonefish & Tarpon Trust, a conservation and fishing nonprofit group.

“When they turned on their lights, fish turned upside down and turned to the bottom,” he said.

In the months that followed, Bucek received reports of upside-down stingrays and lemon sharks swirling violently in the mud. Thousands of species were in trouble, including the critically endangered small sawtooth fish, known for its smooth snout with saw blade-like teeth.

At least 47 sawfish have died, although the number is likely higher, said Michael Crosby, president and CEO of Mote, a nonprofit marine laboratory and aquarium. The toll is profound, since there may only be hundreds of fish left in US waters.

An emergency response to rescue sawmills was launched in early April, involving government agencies and non-profit partners. Meanwhile, scientists at several laboratories are trying to figure out what is causing the widespread distress to marine life.

Recently, tests by researchers identified a cocktail of natural toxins in the seawater and tissues of some affected fish.

“The hypothesis I’m working on right now is that the combination of these different benthic algal toxins are coming together to create the phenomenon we’re seeing,” said Alison Robertson, senior marine scientist at the Dauphin Island Sea Lab.

But that’s not a guarantee, she said, and researchers don’t know what caused the algae bloom or toxins. Moreover, other experts are not so sure.

“I honestly don’t think anything can be reasonably ruled out right now,” Crosby said.

Whatever researchers conclude can ultimately determine what’s on dinner plates at some Florida restaurants, how fishermen make their livings and whether tourists come to visit. The Keys have already experienced several ecological disturbances: Hurricane Irma in 2017, record sea surface temperatures last year and mass coral die-offs.

“We’ve been bouncing from crisis to crisis here,” Bucek said.

Allison Delashmit, executive director of a fishing group called the Lower Keys Guides Association, said “there’s a lot at stake.”

“Our economy is built on tourism. It is no good to have fish swimming on the water and broadcast it without answers about its content,” she said.

That puts a lot of pressure on local scientists to provide answers.

Is algae to blame?

It’s been a tiring eight months for Bucek, whose freezer at home is full of dead fish he plans to send out for testing. He likened the effort to “a final exam that you forgot and never studied for, and you have two hours to learn everything.”

When the work began, he said, the most likely explanations for the strange behavior of the fish were not in a row. Oxygen levels in the water were normal. There were no signs of a red tide. Nothing out of the ordinary was found in pollutant tests.

Boucek thought the exposure was likely from the water, and when he removed spinning fish from the ocean and placed them in tanks of clean water, some were found within 25 minutes.

The only lead was elevated background levels of a genus of algae called Gambierdiscus in water samples.

That clue caught the attention of Michael Parsons, a professor of marine science at Florida Gulf Coast University and an algae expert who has been collecting that genus in the Keys for more than a decade. In February, Parsons discovered that the levels of Gambierdiscus cells were about four times higher than he had ever recorded.

Robertson, an environmental toxicologist, refocused her lab to respond to the crisis and is working seven days a week. She estimates that her team has performed more than 5,000 analyzes of algae, seawater and the muscles, livers, kidneys and stomachs of a variety of affected fish species.

Her work turned up toxins known to affect fish behavior, as well as some new potential toxins never seen before in the Keys.

“What we’re finding in benthic algae, we’re also finding in many fish samples,” Robertson said.

She suspects that a “cocktail” of toxins from seabed algae, which may be from several species, are coming together to cause the fish’s strange behavior, although she said there is “no gun clear tobacco” still exists. The toxins may also be interacting with other environmental toxins, she said.

Attempts to save the saw

Meanwhile, other scientists are racing to help sawdust in distress.

In early April, Mote’s team successfully caught an 11-foot male sawfish swimming in circles in Cudjoe Bay. They loaded the fish onto a boat, took it to a quarantine facility with clean, filtered seawater and infused it with antibiotics, lipid compounds and other treatments, according to Crosby.

“If you can put it in human terms, a patient was brought into intensive care,” he said.

The fish stabilized and “was starting to swim in a more natural pattern,” Crosby said.

But two weeks later, the animal’s health improved and it had to be euthanized.

“Obviously we were going in a positive direction, but the internal organs were just too far,” Crosby said.

He added that he has not seen enough evidence to convince him that algae are to blame. The results of the necropsy (animal autopsy) are still pending, but they could offer important information because researchers were able to run tests shortly after he died. Mote also plans to try to rescue more sawfish.

There are other reasons for hope, too.

Robertson said this episode does not appear to represent an entire ecosystem crash.

Other important species, including barracuda, bonefish and tarpon, are doing well and are largely unaffected, Boucek said.

Florida lawmakers agreed to spend $2 million on fish research in the Keys, which could help scientists find answers faster.

“Because so many scientists are coming together on this issue, we’ll be able to work out what’s going on and come up with mitigation strategies and solutions,” Robertson said.

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