Fishing guides in the Florida Keys began reporting unusual sightings to Ross Boucek last fall. Small baits, especially at night, were beginning to spin in tight circles in the water, seemingly in discomfort.
As the months passed, more reports reached Dr. Boucek, a biologist with the Bonefish & Tarpon Trust, a nonprofit conservation group. Larger fish – walleyes, snook – swam in spirals or upside down in the shallow waters of the Atlantic Ocean and Gulf of Mexico. So are stingrays and the occasional shark.
Dr. Boucek invited scientists to government agencies and universities. They held meetings, took samples of the water and the fish, and tried to understand what could make the fish behave so strangely. Parasite; Sewage leak? Any other pollutant?
Then, in January, the mystery disease began afflicting smalltooth sawfish, a type of large, prehistoric-looking ray named for the snout-like appearance of its peduncle lined with sharp teeth. Sawfish, which are endangered and reliably found only in southernmost Florida, began to die.
The search for answers became urgent, Dr. Boucek said, “as the second most endangered species began to die at an unprecedented rate.”
Now he spends much of his time in a wetsuit, flippers and snorkel, collecting samples and recording data from sensors he deploys along the seabed, looking for changes or patterns that might help solve the mystery.
At least 38 sawfish have died so far this year, according to the Florida Fish and Wildlife Commission, which is investigating the deaths. Perhaps only hundreds of breeding female sawfish remain in the wild, said R. Dean Grubbs, a fish ecologist at Florida State University. The fish can grow up to 18 feet, according to the commission.
A research team led by government scientists scrambled to conduct experiments, glue the sawdust and obtain a blood sample. Florida lawmakers appropriated $2 million in emergency funds to help carry out the project.
Some wonder if last summer’s record-breaking sea temperatures, which bleached coral throughout the Keys, may have altered the ecosystem and caused unusual growth of microalgae.
In their best decision yet, they learned that microalgae that naturally exist near the sea floor have created elevated levels of toxins that strongly affect the neurological systems of fish when they swim in those areas.
This may explain why stranded fish seem to recover when they are raised from the sea floor (where toxin concentrations are higher) to the surface of the water (where concentrations are lower), said Michael Parsons, professor of marine science at the University Florida Gulf Coast. Sawfish are inhabitants of the bottom of the sea.
Since early April, the National Marine Fisheries Service has been trying to rescue and rehabilitate sawfish spotted at risk, a logistically daunting effort the agency calls the first of its kind in the United States. The group rescued its first sawfish, an 11-foot male, on April 5 after a member of the public saw it swimming in circles in Cudjoe Bay. He is now recovering at the Mote Marine Laboratory & Aquarium in Sarasota, with the hope that he can eventually be returned to the wild.
Since the start of the crisis, more than 150 sick sawmills have been observed. Whirling sawfish have been spotted as far north as Palm Beach County, but scientists have not linked their behavior to that of the fish in the Lower Keys.
Gregg Furstenwerth, who lives on Little Torch Key and has been spotting fish spinning for months by sharing videos on social media, said he saw a sawfish, about 14 feet long, late last month on a beach near Key West .
“My wife started crying,” he said. “I wish it was better. I’m sitting here watching the ecosystem fall apart and I’m powerless to stop it.”
What’s happening threatens not only endangered sawfish and other marine life — about 426 dead fish from more than 50 species have been reported in the state — but also the livelihoods of many in the Lower Keys whose jobs are tied to sport fishing.
Some fishing guides have had clients cancel their trips because they are concerned that because people are worried that the fish they catch will not be safe to eat, Dr. Boucek said. The state says people should not consume any fish that have exhibited abnormal behavior.
One of the microalgae species identified, Gambierdiscus, produces several toxins, including a compound responsible for a common form of fish poisoning in humans called ciguatera. But it usually doesn’t make the fish sick.
“It’s been a stressful few months, just trying to piece together a very complicated puzzle,” said Allison Delashmit, executive director of the Lower Keys Guides Association.
More than one thing could be to blame for the sick and dying fish, warned Alison Robertson, an associate professor of marine sciences at the University of South Alabama. Fish in the Keys, where many toxins have been present for years, may be predisposed to abnormal behavior due to previous exposure.
“We believe that the combined effect of multiple toxins is causing the behavioral effects we have seen,” Dr Robertson said.
To collect new data, Dr. Boucek, 39, who lives on a sailboat in Marathon, Middle Keys, goes out on a boat every few days to check the sensors.
On a recent morning, Capt. Nick LaBadie, a 33-year-old fishing guide, took Dr. Boucek at six locations around Sugarloaf Key, about 15 miles north of Key West, reading GPS coordinates to track sensors located by floating buoys. The first site, nicknamed Tarpon Belly, was where some of the first spinning fish had been reported, Dr Butcek said.
“You talk to these guys who are 70 years old and they’re like, ‘I’ve never seen this before,'” he recalls.
He put on his bathing suit and stepped in, squealing “Whoah!” as the cold water hit. He cleaned the tip of one sensor and opened another. He could see clearly down to the shallows, but still saw the bull sharks, which he and Mr. LaBadie agreed can be “pretty wild.”
Back on the boat, Dr. Boucek recorded his work by hand, in pencil. He added fixative to preserve a sample of water and placed it in a refrigerator.
“Every day, you think you have a pattern, and the next week that pattern is completely gone,” he said.
He failed to find a sensor in another spot where the water was more cloudy. But Dr. Bucek noted promising signs such as a nurse shark and a red snapper at Sugarloaf Marina, where few fish had been seen for a while. Near Tarpon Belly, he spotted “mullet slime,” a dark patch created when he was feeding on fish on the seabed, for the first time this season.
He didn’t find any sawfish.
However, shortly after the boat docked and left the marina, word spread among fishing guides and scientists: A threshing sawfish had washed up on a beach in Key West. Tourists watched it die.
Kitty Bennett contributed to the research.
