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An unprecedented US federal effort to rescue and rehabilitate endangered smalltooth sawfish is getting underway this week in the Florida Keys, where unusual and concerning behavior has been documented, including spinning and whirling—signs the fish are in distress.

Some 32 of the sawfish have been reported dead, although the number is believed to be higher, because the fish tend to sink after death. The smalltooth sawfish, in 2003, was the first marine fish to be listed as endangered under the US Endangered Species Act. In the United States, the range of the animal named for its distinctive rostrum, which is shaped like a saw, once spanned coastal waters from Texas to North Carolina; today, sawfish are found only in South Florida.

“From a recovery standpoint, we’re alarmed that it could have long-term effects on the population’s ability to recover,” says Adam Brame, sawfish recovery coordinator for the National Marine Fisheries Service, an office of the National Oceanic and Atmospheric Administration. The service is the lead agency in the rescue and rehabilitation effort. “It’s an unprecedented event, and I would like to say it’s an unprecedented response by the agency,” Brame says.

The unusual behavior and deaths began in January 2024, affecting large juvenile and adult sawfish in the three- to 4.5-meter range, although as many as 40 other fish species have exhibited similar actions since November 2023. The fish are swimming erratically, in circles and upside down. Some are beaching themselves in shallow waters, Brame says.

“This behavior has never been seen in sawfish before,” says Brame, who has worked in sawfish recovery for nine years. “We’ve never seen mortality to this scale and to this duration in time.”

The problems were centered in the lower Florida Keys, although the affected area appears to be expanding north to include waters that are within close proximity to Everglades National Park, part of a watershed that is the focus of a multi-billion-dollar federal and state restoration effort.

“We don’t know if the animals are moving out of the area that has the affected water or if the affected water is spreading,” says Tonya Wiley, president of Havenworth Coastal Conservation, a nonprofit organization involved in the rescue and rehabilitation effort.

This portion of southern Florida was affected in summer 2023 by a record marine heat wave that stressed sensitive coral reefs, leading to widespread bleaching.

A smalltooth sawfish swims circles in the shallow waters of the Florida Keys. Video courtesy of the Florida Fish and Wildlife Conservation Commission

It is not clear whether the calamities are related. Water temperature, salinity, and dissolved oxygen do not appear to be factors in the sawfish event, according to the Florida Fish and Wildlife Conservation Commission, which is leading the investigation into their plight. Necropsies conducted by the agency have found no evidence of a communicable pathogen or bacterial infection. Toxins associated with red tide have not been detected in water samples.

The rescue and rehabilitation effort is the latest in Florida. Last summer’s bleaching event sparked a rush to rescue ailing corals from dangerously hot waters and relocate them to on-land tanks. Thousands of corals were removed from the Florida Keys National Marine Sanctuary, which includes the only barrier reef in the continental United States.

Nearly 2,000 manatees died in the state in 2021 and 2022, a two-year record. The die-off prompted the US Fish and Wildlife Service and Florida Fish and the Wildlife Conservation Commission to go so far as to provide supplemental lettuce for starving manatees in the Indian River Lagoon, a crucial manatee habitat on the state’s east coast. Ongoing water quality problems there have led to a widespread loss of seagrass, the sea cows’ primary food. Aquariums, zoos, and other rehabilitation facilities scrambled to take in the emaciated manatees.

The sawfish effort is unusual because, unlike manatees, which can be transported in vans and trucks, the massive fish must remain submerged to breathe, a fact posing big challenges for the collaborators involved in their rescues. The effort also includes the Florida Fish and Wildlife Conservation Commission and Mote Marine Laboratory and Aquarium, among other partners.

The puzzle of how to relocate the sawfish remains under discussion; possibilities include in-water towing vessels, Brame says. The National Marine Fisheries Service says never has there been such an attempt to rescue and rehabilitate smalltooth sawfish from the wild.

The cost of these efforts hasn’t been calculated, and Wiley says most of the partners already have spent through their reserves and now are scrambling to raise money for their emergency work.

The plan is to move the animals to quarantined tanks where they can receive around-the-clock care. After that, it is uncertain whether the sawfish will be returned to where they were collected from, if the problem affecting them proves to be environmental, Brame says.

“It’s really hard because it’s a species that I’ve been working on for over two decades, and this is the singular most devastating event that we’ve had for sawfish,” Wiley says. “To not know what is causing it yet, it’s really hard. We’ve lost a lot of sleep. We’re all very taxed, and that’s why we launched this effort to rescue and rehab them. We couldn’t just sit by and watch them die.”