Fishing guides in the Florida Keys began reporting unusual sightings to Ross Boucek last fall. Especially at night, the small bait fish began spinning in tight circles in the water as if in distress.
As the months passed, more reports came in to Dr. Boucek, a biologist with the Bonefish & Tarpon Trust, a non-profit conservation organization. Larger fish (jacks, snook) were swimming spirally or upside down in the shallow waters of the Atlantic and Gulf of Mexico. So were stingrays and the occasional shark.
Dr. Boucek called scientists from state agencies and universities. They held meetings and took samples of water and fish to try to figure out what was making the fish behave so strangely. helminth? Sewage spill? Other contaminants?
Then, in January, a mysterious disease began plaguing the smalltooth sawfish. These are large, prehistoric-looking stingrays that are named for the shape of their snout-like snouts lined with sharp teeth. The sawfish, which is critically endangered and can only be found reliably in southern Florida, is beginning to die off.
Finding answers has become urgent, Dr. Boucek said. “This is the moment when endangered species begin to disappear at an unprecedented rate.”
He now dons a wetsuit, flippers and snorkeling mask and spends much of his time collecting samples from sensors placed on the ocean floor, recording data and looking for changes or patterns that could help solve mysteries.
At least 38 sawfish have died this year, according to the Florida Fish and Wildlife Commission, which is investigating the causes of death. Perhaps only a few hundred 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 long, according to the commission.
Research teams led by state scientists raced to conduct experiments, tag sawfish and take blood samples. Florida lawmakers designated $2 million in emergency funding to help get the work done.
Some wonder whether last summer's record ocean temperatures that bleached coral reefs across the Keys may have altered the ecosystem and triggered unusual microalgae growth.
As best they can so far, they've learned that microalgae naturally present near the seafloor produce high levels of toxins that have serious effects on the nervous systems of fish when they swim into the area.
This may explain why spinning fish appear to recover when pulled from the seafloor (where toxin concentrations are high) to the surface (where toxin concentrations are low), said Michael Parsons, a professor of marine science at Florida Gulf Coast University. The sawfish is a creature that lives on the sea floor.
Since early April, the National Marine Fisheries Service has been working to rescue and rehabilitate sawfish in distress. This is a logistically challenging endeavor, the agency's first in the United States. The team rescued their first sawfish, an 11-foot male, on April 5 after members of the public spotted it swimming in circles in Cudjoe Bay. He is currently recovering at the Mote Marine Laboratory & Aquarium in Sarasota and hopes to eventually be released back into the wild.
More than 150 sick sawfish have been observed since the crisis began. Swirling sawfish have been found as far north as Palm Beach County, but scientists have not linked their behavior to that of fish in the Lower Keys.
Gregg Furstenwerth, who lives on Little Torch Key and has been spotting the spinning fish for months and sharing videos on social media, said he spotted a sawfish, about 14 feet long, off a beach near Key West late last month.
“My wife started crying.” He said. “I wish she was better. “I sit here and watch the ecosystem collapse on itself, and I am powerless to stop it.”
Whatever happens, it threatens not only the endangered sawfish and other marine life (about 426 dead fish from more than 50 species have been reported to the state), but also the livelihoods of many people in the Lower Keys whose jobs involve sport fishing. .
Some fishing guides have asked clients to cancel trips because people are worried the fish they catch will not be safe to eat, Dr. Boucek said. The state says people should not eat fish that exhibit abnormal behavior.
One of the discovered microalgae species, Gambierdiscus, produces several toxins, including ciguatera, the compound responsible for common fish poisoning in humans.
“It’s been a stressful few months, putting together a very complex puzzle,” said Allison Delashmit, executive director of the Lower Keys Guides Association.
There may be multiple culprits for sick and dying fish, warned Allison Robertson, associate professor of marine sciences at the University of South Alabama and senior marine scientist at the Dauphin Island Marine Laboratory. Fish in the Keys, where numerous toxins have been present for many years, may have a tendency to behave abnormally due to previous exposure.
“We think it’s actually the combined effect of multiple toxins that causes the behavioral effects we’ve seen,” Dr. Robertson said.
To collect new data, Dr. Boucek, 39, who lives on a sailboat in Marathon in the Middle Keys, goes out on his boat every few days to check the sensors.
One recent morning, Capt. Nick LaBadie, a 33-year-old fishing guide, took Dr. Boucek to six locations around Sugarloaf Key, about 15 miles north of Key West, to read GPS coordinates and track sensors identified as floating buoys. The first site, nicknamed Tarpon Belly, is where some of the first spinning fish were reported, Dr. Boucek said.
“When I talk to 70-year-olds, they say, ‘I’ve never seen this before,’” he recalled.
He put on his swimming gear and jumped in, screaming “Oooh!” When he hits the cold water. He cleaned the tip of one sensor and placed the other. He could clearly see all the way to the shallow bottom, but was still wary of bull sharks. He and Mr LaBadie agreed that bull sharks can be “very aggressive”.
Back on the ship, Dr. Boucek recorded his work by hand in pencil. To preserve the water samples, he added fixative and stored them in a cooler.
“I thought there was a pattern every day, and then the next week that pattern was completely gone,” he said.
He didn't find the sensors in other places where the water was more murky. But Dr. Boucek pointed out promising signs, including nurse sharks and red snapper at Sugarloaf Marina, which has seen few fish for some time. For the first time this season, near Tarpon Belly, he discovered “mullet mud,” a dark patch created when the fish are fed and the seabed is stirred.
He never encountered a sawfish.
But not long after docking the boat and leaving the dock, word spread among fishing guides and scientists that a struggling sawfish had washed up on a beach in Key West. Tourists watched it die.
kitty bennett contributed to the research.