Why are Florida fish spinning and dying? Scientists have a suspect

A mysterious disease causes Fish in the Florida Keys run in circles It has launched a frantic race to find the cause and save endangered species before it is too late.

After eight months of chasing scientists, some believe the main suspect has emerged: toxins from algae that colonize the seafloor may cause neurological problems for some species of fish.

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

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

Over the following months, Busick received reports of upside-down stingrays and lemon sharks circling violently in the mud. Dozens of species were affected, including the endangered smalltooth sawfish, known for its flat snout and saw-blade-like teeth.

at least 47 sawfish killedAlthough the number is likely higher, said Michael Crosby, president and CEO of Mote, a nonprofit marine laboratory and aquarium. The losses are great, given the possibility of their existence alone Several hundred fish were left in American waters.

An emergency response to rescue the stricken sawfish was launched in early April, involving government agencies and nonprofit partners. Meanwhile, scientists in several laboratories are trying to figure out the cause of the widespread distress of marine life.

Recently, researchers’ tests identified a mixture of natural toxins in seawater and the tissues of some distressed fish.

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

She added that this is not a confirmation, and researchers do not know the cause of the algae blooms or the toxins. In addition, other experts are less convinced.

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

Whatever the researchers ultimately conclude may determine what’s on dinner plates at some Florida restaurants, how fishermen earn their livelihoods, and whether tourists come to visit. The Keys have already suffered several environmental shocks: Hurricane Irma in 2017, record sea surface temperatures last year, and the mass die-off of coral reefs.

“We’ve been going from crisis to crisis here,” Busick said.

“There’s a lot at stake,” said Allison Delashmidt, executive director of a hunting group called the Lower Keys Guides Association.

“Our economy is built on tourism. It’s not good to just spin fish on the water and spit them out without answers about what they are,” she said.

This puts local scientists under intense pressure to provide answers.

Are algae to blame?

It’s been a tiring eight months for Busick, whose refrigerator at home 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, the most likely explanations for the fish’s strange behavior had yet to be found, he said. Oxygen levels in the water were normal. There were no signs of red tide. Tests for contaminants found nothing out of the ordinary.

Busiek thought the exposure was likely to the water, and when he took the spinner fish out of the ocean and placed them in tanks with clean water, some of them recovered in less than 25 minutes.

The only lead was high background levels of an algae genus called Gambierdiscus in the water samples.

This evidence caught the attention of Michael Parsons, a professor of marine sciences at Florida Gulf Coast University and an algae expert who has been collecting this species in the Keys for more than a decade. In February, Parsons discovered that Gamberdiscus cell levels were about four times higher than he had ever recorded.

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

Her work has uncovered toxins known to affect fish behavior, as well as some new potential toxins that have never been seen before 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 seafloor algae, possibly from several species, combine to cause the fish’s strange behavior, although she said there is still no “clear conclusive evidence.” She said the toxins can interact with other environmental toxins as well.

Sawfish rescue efforts

Meanwhile, other scientists are racing to help the stricken sawfish.

In early April, Mote staff rescued an 11-foot sawfish that was swimming in circles in Cudjoe Bay. They loaded the fish onto a boat, transported it to a quarantine facility with clean, filtered seawater, and then injected it with antibiotics, lipid compounds and other treatments, according to Crosby.

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

The fish settled down and “began swimming in a more normal pattern,” Crosby said.

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

“We were clearly headed in a positive direction, but the internals were a long way off,” Crosby said.

He added that he had not seen enough evidence to convince him that algae was responsible. The results of the necropsy (an autopsy of an animal) are still pending, but they could provide important information because researchers were able to conduct tests shortly after its death. Mote also plans to try to save more sawfish.

There are other reasons for hope, too.

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

Other important species are doing well, including barracuda, bonefish and tarpon, which appear to have been largely unaffected, Busick said.

Florida lawmakers have also agreed He spent $2 million on fish research in the KeysWhich may help scientists reach answers more quickly.

“Because many scientists are coming together on this issue, we will be able to figure out what is happening and find strategies and solutions to mitigate its effects,” Robertson said.

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