Florida Keys Spinning Fish Update

In October of 2023, Ross Boucek, Director of the Florida Keys Initiative with Bonefish Tarpon Trust (BTT), started receiving calls about strange fish behavior from his fishing partners and friends. Little did he know this event would continue for years, gaining widespread media attention as a rare and unexplainable phenomenon plaguing South Florida’s beloved sea life. Today, fishermen and scientists are still baffled by this unusual occurrence and closely monitor for trends from last year’s casualties. 

Although the culprit behind the spinning fish is not yet proven, there are some leading suspects, major trends, and years of data that offer evidence that it may be slowing down. The operation leader in Miami-Dade and Monroe counties, Ross Boucek, breaks down his first-hand encounters of the sick fish since the very beginning.

“It was so unusual that we initially thought a couple of fish were having a bad day, but as we reached the next month, it was clear that things were getting worse,” Boucek recalled. By December 2023, BTT partnered with the Florida Fish and Wildlife Conservation Commission (FWC) to bring experts in ecotoxicology and harmful algal blooms on the case.

Within a week, Dr. Mike Parsons observed extremely high concentrations of Gambierdiscus in the water, a harmful algal bloom linked to ciguatoxin, which causes gastrointestinal and neurological symptoms in humans. Boucek continued, “The casualties peaked in March of 2024, with a drop-off in the summer. As the temperature increased, the mortalities just disappeared.” The timeline indicates that the mortalities climaxed in 70-degree water, the same tolerance window for Gambierdiscus. Yet, the dying fish were sampled and showed no signs of ciguatera poisoning- a missing link that adds another layer of abnormality. 

“Harmful algae species are tricky,” Boucek explained. “Their effects can depend on their abundance, but also how toxic individual cells become. The easiest way to explain it is that they get grumpy when it’s too hot or too cold.” The only other trend observed was that the fish were predominantly dying in localized inshore areas between Islamorada and the lower Keys. No conclusion prevailed.

As temperatures dropped again in late 2024, researchers braced for a potential resurgence. “We had no idea what to expect,” Boucek admitted. “When you go from zero to extreme, it’s hard to forecast what happens next.”

While reports have increased slightly, they remain well below last year’s levels. From December 2024 to February 2025, only 30 reports of spinning fish were recorded - compared to 74 during the same period the year before. Boucek also notes that the current spinning fish reports appear in only half of the species that were symptomatic before, suggesting some fish may be more sensitive to the ailment than others. 

Sawfish, an already endangered species, appears to be one of the most sensitive, raising questions about how authorities should offset the fatalities. Boucek offers solutions, “We can invest in veterinary options and science or, at the extreme end, partner with aquariums to hold sawfish. But ultimately, it’s going to be a matter of how much the state and federal government are willing to pay to save them.” A somber statement for the current state of federal funding. 

Just as only time will tell the fate of the smalltooth sawfish, scientists will have to wait to understand the full cause and scope of the abnormality. “Now we’re in the slow burn phase of science where experiments take time to run thorough analyses,” Boucek explained. Experts remain cautiously optimistic; so far this year’s data is promising. 

“There’s a couple of localized hotspots where we’re seeing spinning fish, but nothing to the intensity that we saw last year,” said Boucek. In fact, exclusively healthy sawfish have been caught in Florida Bay, and 2025 continues to be one of the best years of Florida Keys inshore fishing for tarpon and bonefish. 

Overall, many questions remain about the spinning fish sickness. BTT is working diligently with partners to answer the lingering mysteries through their collaborative research efforts with the Lower Keys Guides Association, Florida International University, Florida State University, and the FWC. Boucek commented on the collaboration, “If it wasn’t for the fishing community, our progress would’ve been severely halted. Because they’re out on the water every day, BTT was able to get a three-month head start on research, which is invaluable when time is our most precious commodity.”

Bonefish Tarpon Trust will continue to partner with local fishing guides through a Rapid Response Network to track the spread and intensity of the phenomenon throughout 2025. For now, Boucek stresses the importance of saving the species that have been severely affected. “Sawfish are Florida’s iconic marine species- we can’t lose them. This event really showcases the urgency of pumping more money into sawfish research because when we save the sawfish, it trickles down to saving our entire ecosystem.”  

While it is still unknown if human causes are tied to the fish sickness, Boucek emphasizes there are general practices that prove to be helpful in maintaining a healthy marine habitat. “What we can do is push effort into the things that can be fixed. We have to make sure that ecosystem processes are functioning and water quality is good.” 

Boucek and his team at Bonefish and Tarpon Trust are committed to working alongside researchers, agencies, and the fishing community to uncover the full scope of this crisis. The waters of the Florida Keys hold more questions than answers, but with every sample collected, every report analyzed, and every sawfish saved, scientists move one step closer to unraveling one of the most bizarre marine mysteries in recent history.