ReeferA
New Member
Fish along the Florida Keys are spinning in circles until they die—and no one knows why
In the middle of the night in November 2023, scuba diver Gregg Furstenwerth shone his flashlight on a fish swimming through a seagrass meadow in the Florida Keys.
What he saw surprised him: The distressed pinfish was spinning and whirling in upside-down circles. Puzzled, he recorded the behavior with his underwater camera.
When he heard more and more similar reports of spinning fish from friends and other divers, Furstenwerth began to document more incidents, both from his boat and from walking docks at night.
At first, the sightings occurred mostly along a 35-mile stretch of water in the lower Keys, a tropical archipelago of islands south of mainland Florida. Then, three reports surfaced in Miami, according to conservation group Bonefish Tarpon and Trust, and most recently, one case in the upper Keys.
As of March 2024, locals and scientists have identified the bizarre actions in at least 44 species, including the critically endangered smalltooth sawfish. Many fish have been washing up dead, though there's not a formal count, according to the Florida Fish and Wildlife Conservation Commission.
The cause of the sick fish is unknown, prompting a collaborative investigation among various universities, institutes, and state agencies in a race to identify the culprit.
“Everybody wants to know what it is right now,” says Alison Robertson, a marine scientist who studies harmful algal blooms at the University of South Alabama's Stokes School of Marine and Environmental Sciences and the Dauphin Island Sea Lab.
"We're going to do everything we possibly can to work together to try and identify that so we can come up with solutions,” she says. “It is very strange to see such a prolonged event affecting so many different species.”
Possible causes include harmful algal blooms, which can produce neurotoxins that impact fish behavior; pollutants; environmental factors such as low oxygen or high temperature; diseases; and parasites. (See photos of extreme algal blooms worldwide.)
"It's hard to process," Furstenwerth says of the ailing fish he's witnessed. "I must keep doing this though—it's not in my nature to quit."
Red tides occur when microscopic algae, a type of phytoplankton, suddenly bloom in large numbers along a coastal area, releasing natural toxins into the water that can harm wildlife and even people.
But in this recent case, it wasn’t. There was no evidence of a red tide in the Keys, nor were there low oxygen levels, high temperatures, or parasites on the dead fish, according to Kelly Richmond of the fish and wildlife commission. (Learn more about threats to oceans and marine life.)
Robertson, Parsons, and colleagues are investigating the presence of natural algal toxins in ocean water, sediment, algae, and a variety of fish taken from the Keys.
For instance, water samples showed higher than normal levels of a type of seafloor-dwelling algae in the genus Gambierdiscus. Normally, a liter of Keys water contains 30 to 40 Gambierdiscus cells; recent samples from affected areas contained about a thousand. Some harvested fish contained ciguatoxins, which also come from Gambierdiscus; and others carried okadaic acid, produced by another type of bottom-dwelling seaweed.
Ciguatera is more common in reef areas that are environmentally stressed, and the Keys face myriad problems, including warming waters that cause coral bleaching, water pollution, and coastal development.
Next, the scientists plan to expose laboratory fish to water collected from areas in Big Pine Key, where spinning fish have been observed. If these fish begin spinning within six to 12 hours, that water will be tested for toxins. They'll compare these results with another experiment in which fish are exposed to toxins added to artificial seawater at levels similar to those found in the Keys. (Learn about new diseases and toxins harming marine life.)
The experiments "will help us confirm or rule out the contribution of these algae and their toxins to the fish behaviors observed in the Keys," Parsons says.
A team from the nonprofit Ocean First Institute also plans to compare blood samples from sharks taken prior to reports of the spinning fish phenomenon with those taken more recently. The goal is to figure out any long-term health effects in shark species that have displayed the odd behavior, as well as investigate how the mysterious condition occurs in the body, says Chris Malinowski, the institute's director of research and conservation.
“Fish kills happen, unfortunately, all over the place,” Parson adds. “But in this case, we can't explain it by the usual causes. That's the strangeness of this event.”
As of early March, 21 sawfish have washed up dead, with reports of up to 60 distressed individuals, says Dean Grubbs, a fish ecologist at Florida State University who studies the species. On March 13, a distressed sawfish was spotted at Boynton Beach, roughly 200 miles north—a "disturbing" discovery so far north, he says.
“From the sawfish perspective, it's obviously a big concern just to have this many large animals die,” Grubbs says.
While smalltooth sawfish—which can reach lengths of 12 feet—historically occurred on both sides of the Atlantic, only two populations remain in the Bahamas and the U.S., the latter being larger. “That means the recovery of the species is pretty much dependent on the U.S. population,” Grubbs says.
“I don't think we have any clue yet whether this is something that will be over in a year, and we won't even know it happened, or [if it's] potentially catastrophic,” he says. “My hope for spreading the word is just that it gets out to more brain power."
In the middle of the night in November 2023, scuba diver Gregg Furstenwerth shone his flashlight on a fish swimming through a seagrass meadow in the Florida Keys.
What he saw surprised him: The distressed pinfish was spinning and whirling in upside-down circles. Puzzled, he recorded the behavior with his underwater camera.
When he heard more and more similar reports of spinning fish from friends and other divers, Furstenwerth began to document more incidents, both from his boat and from walking docks at night.
At first, the sightings occurred mostly along a 35-mile stretch of water in the lower Keys, a tropical archipelago of islands south of mainland Florida. Then, three reports surfaced in Miami, according to conservation group Bonefish Tarpon and Trust, and most recently, one case in the upper Keys.
As of March 2024, locals and scientists have identified the bizarre actions in at least 44 species, including the critically endangered smalltooth sawfish. Many fish have been washing up dead, though there's not a formal count, according to the Florida Fish and Wildlife Conservation Commission.
The cause of the sick fish is unknown, prompting a collaborative investigation among various universities, institutes, and state agencies in a race to identify the culprit.
“Everybody wants to know what it is right now,” says Alison Robertson, a marine scientist who studies harmful algal blooms at the University of South Alabama's Stokes School of Marine and Environmental Sciences and the Dauphin Island Sea Lab.
"We're going to do everything we possibly can to work together to try and identify that so we can come up with solutions,” she says. “It is very strange to see such a prolonged event affecting so many different species.”
Possible causes include harmful algal blooms, which can produce neurotoxins that impact fish behavior; pollutants; environmental factors such as low oxygen or high temperature; diseases; and parasites. (See photos of extreme algal blooms worldwide.)
"It's hard to process," Furstenwerth says of the ailing fish he's witnessed. "I must keep doing this though—it's not in my nature to quit."
Ruling out culprits
“When you have distressed fish or a fish kill in Florida, the first thing people will think about… is a red tide,” says Michael Parsons, a marine ecologist who studies algal blooms at Florida Gulf Coast University.Red tides occur when microscopic algae, a type of phytoplankton, suddenly bloom in large numbers along a coastal area, releasing natural toxins into the water that can harm wildlife and even people.
But in this recent case, it wasn’t. There was no evidence of a red tide in the Keys, nor were there low oxygen levels, high temperatures, or parasites on the dead fish, according to Kelly Richmond of the fish and wildlife commission. (Learn more about threats to oceans and marine life.)
Robertson, Parsons, and colleagues are investigating the presence of natural algal toxins in ocean water, sediment, algae, and a variety of fish taken from the Keys.
For instance, water samples showed higher than normal levels of a type of seafloor-dwelling algae in the genus Gambierdiscus. Normally, a liter of Keys water contains 30 to 40 Gambierdiscus cells; recent samples from affected areas contained about a thousand. Some harvested fish contained ciguatoxins, which also come from Gambierdiscus; and others carried okadaic acid, produced by another type of bottom-dwelling seaweed.
Ciguatera is more common in reef areas that are environmentally stressed, and the Keys face myriad problems, including warming waters that cause coral bleaching, water pollution, and coastal development.
Testing for toxins
If people eat fish with high levels of ciguatoxins, they can contract ciguatera, a type of illness that causes vomiting, nausea, and neurological symptoms. In previous laboratory experiments, fish that ate food with ciguatoxins displayed neurological deficits including hyperactivity and twitching.Next, the scientists plan to expose laboratory fish to water collected from areas in Big Pine Key, where spinning fish have been observed. If these fish begin spinning within six to 12 hours, that water will be tested for toxins. They'll compare these results with another experiment in which fish are exposed to toxins added to artificial seawater at levels similar to those found in the Keys. (Learn about new diseases and toxins harming marine life.)
The experiments "will help us confirm or rule out the contribution of these algae and their toxins to the fish behaviors observed in the Keys," Parsons says.
A team from the nonprofit Ocean First Institute also plans to compare blood samples from sharks taken prior to reports of the spinning fish phenomenon with those taken more recently. The goal is to figure out any long-term health effects in shark species that have displayed the odd behavior, as well as investigate how the mysterious condition occurs in the body, says Chris Malinowski, the institute's director of research and conservation.
“Fish kills happen, unfortunately, all over the place,” Parson adds. “But in this case, we can't explain it by the usual causes. That's the strangeness of this event.”
Endangered species at risk
Of particular concern is the smalltooth sawfish, which have been listed on the U.S. Endangered Species Act since 2003 due to coastal development and bycatch. It’s one of just five species of sawfish globally, and the only one in U.S. waters. (Read: "Searching for the world's last remaining sawfish.")As of early March, 21 sawfish have washed up dead, with reports of up to 60 distressed individuals, says Dean Grubbs, a fish ecologist at Florida State University who studies the species. On March 13, a distressed sawfish was spotted at Boynton Beach, roughly 200 miles north—a "disturbing" discovery so far north, he says.
“From the sawfish perspective, it's obviously a big concern just to have this many large animals die,” Grubbs says.
While smalltooth sawfish—which can reach lengths of 12 feet—historically occurred on both sides of the Atlantic, only two populations remain in the Bahamas and the U.S., the latter being larger. “That means the recovery of the species is pretty much dependent on the U.S. population,” Grubbs says.
“I don't think we have any clue yet whether this is something that will be over in a year, and we won't even know it happened, or [if it's] potentially catastrophic,” he says. “My hope for spreading the word is just that it gets out to more brain power."
Last edited:
