TAMPA, Fla. — A devastating occurrence has been puzzling scientists since last fall: endangered sawfish in the Florida Keys exhibiting abnormal behaviors before dying. These creatures, notable for their elongated, toothed snouts that resemble a saw, were involved in what researchers are calling an “unusual mortality event.”
With the National Oceanic and Atmospheric Administration initiating an emergency response in March, researchers have tirelessly sought the cause behind the deaths of 54 sawfish. Recent findings suggest the likely culprits are various toxins acting in tandem, according to scientists studying the phenomenon.
The investigation has ruled out several potential causes for the sawfish’s erratic behavior and subsequent deaths, including water quality aspects like oxygen levels, salinity, pH, and temperatures. Notably, the dreaded red tide algae blooms were also discounted as a factor.
The breakthrough came when researchers identified unusually high concentrations of dinoflagellates — microscopic algae known for producing harmful toxins — in the local waters. Michael Parsons, a marine ecologist at Florida Gulf Coast University, first made this discovery, highlighting the presence of elevated dinoflagellate levels that produce ciguatoxin, a neurotoxin harmful to both fish and humans. In humans, this toxin can cause nausea, vomiting, and neurological issues.
Further research led by marine scientist Alison Robertson has found these toxins present in the liver and gill tissues of affected sawfish. This suggests that the sawfish, which typically feed near the ocean floor, were likely exposed to this toxin by filtering water containing the algae or through consuming contaminated prey.
As observers reported seeing affected sawfish display unusual spinning behaviors, researchers closely monitored these events throughout the region. Efforts to understand and mitigate the phenomenon included the rescue attempt of a critically ill sawfish by Mote Marine Laboratory and Aquarium in May, although the fish sadly had to be euthanized due to its declining condition.
Despite these challenges, there was a reported decrease in the number of occurrences in May, suggesting a waning phase of the toxic algae bloom or adaptation by local marine life.
Gill McRae, director of the Fish and Wildlife Research Institution, emphasized the probative value of ongoing research into these events. “The evidence increasingly suggests a naturally occurring algal species producing neurotoxins, which is consistent with the neurological symptoms observed in these fish,” McRae explained.
Local authorities and research organizations are encouraging the public to report any sightings of sawfish — healthy, sick, or deceased — to increase data collection and aid in the recovery efforts for this endangered species. Reports on unusual fish behavior or mortality can also be directed to the state’s hotline.
These findings not only aid in protecting the endangered sawfish but also serve as crucial indicators of the health of marine ecosystems in the Florida Keys, which are essential for biodiversity and local fisheries. As research continues, the case of the sawfish deaths underscores the vital connection between environmental stewardship and wildlife conservation.