A prime suspect has emerged in the mystery of Florida’s bizarre spinning fish

A mysterious condition that causes fish in the Florida Keys to spin in circles has sparked a frantic race to find the cause and save an endangered species before it’s too late.

After eight months of research by scientists, some think a prime suspect has emerged: toxins from algae that colonize the seabed can cause neurological problems in some fish species.

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

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

Over the next few months, Boucek received reports of upside-down stingrays and lemon sharks swirling violently through the mud. Dozens of species were affected, including the critically endangered smalltooth sawfish, known for its flat snout with teeth that resemble a saw blade.

At least 47 sawfish have died, although the number is likely higher, said Michael Crosby, the president and CEO of Mote, a nonprofit marine laboratory and aquarium. The toll is enormous, as only a few hundred fish may remain in U.S. waters.

An emergency response effort was launched in early April to save stricken sawfish, involving government agencies and nonprofit partners. Meanwhile, scientists from several labs are trying to figure out what’s causing the widespread distress to marine life.

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

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

But that’s not confirmation, she added, and researchers don’t know what allowed the algae or toxins to multiply. Moreover, other experts are less convinced.

“I honestly don’t think anything can reasonably be ruled out at this point,” Crosby said.

Whatever researchers ultimately conclude could determine what’s on the plate at some Florida restaurants, how fishermen make their living and whether tourists visit. The Keys have already suffered several ecological shocks: Hurricane Irma in 2017, record sea surface temperatures last year and mass coral die-offs.

“We’re bouncing from crisis to crisis here,” Boucek said.

Allison Delashmit, executive director of a fishing group called the Lower Keys Guides Association, said, “The stakes are high.”

“Our economy is built on tourism. It is not a good look to have fish spinning on the water and broadcasting it without answers as to what it is,” she said.

This puts great pressure on local scientists to provide answers.

Is it the algae’s fault?

It’s been an exhausting eight months for Boucek, whose home freezer is filled with dead fish that he plans to send for testing. He compared the effort to “a final exam that you forgot and never studied before, and you have two hours to learn everything.”

When the work began, he said, the most likely explanations for the bizarre fish behavior did not emerge. The oxygen level in the water was normal. There were no signs of red tide. Tests for contaminants turned up nothing unusual.

Boucek thought the exposure likely came from the water, and when he removed the spinning fish from the ocean and placed them in tanks of clean water, some recovered in just 25 minutes.

The only clue 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 had been collecting that same genus in the Keys for more than a decade. In February, Parsons discovered that levels of Gambierdiscus cells were about four times higher than he had ever measured.

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

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

“The things we find in benthic algae, we also find in a lot of fish samples,” Robertson said.

She suspects that a “cocktail” of toxins from algae on the seabed, possibly from different species, combine to cause the fish’s strange behavior, although she said there is still “no obvious smoking gun.” The toxins can also interact with other environmental toxins, she said.

Attempts to save the sawfish

Other scientists, meanwhile, are rushing to help distressed sawfish.

In early April, Mote staffers rescued a 10-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 gave it antibiotics, lipid compounds and other treatments, Crosby said.

“If you can put it in human terms, we moved a patient to intensive care,” he said.

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

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

“We were clearly moving in a positive direction, but the internal organs were too far gone,” Crosby said.

He added that he hasn’t seen enough evidence to convince him that algae is to blame. The results of the necropsy (an autopsy of an animal) are still pending, but they could provide important information because researchers were able to perform tests shortly after death. Mote also plans to save more sawfish.

There are other reasons for hope too.

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

Other key species are doing well, including barracuda, bonefish and tarpon, which appear to be largely unaffected, Boucek said.

Florida lawmakers also agreed to spend $2 million on fish research in the Keys, helping scientists get answers faster.

“Because so many scientists are coming together in this area, we will be able to figure out what’s going on and find mitigation strategies and solutions,” Robertson said.

This article was originally published on NBCNews.com

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