Scientists are blaming toxic algae for spinning behavior and death in Smalltooth Sawfish in the Florida Keys. Fishing guides first reported fish showing erratic behavior in October 2022, fuelling the FWC to take water samples and test pH, salinity, temperature, and dissolved oxygen levels.
Harmful Algae Blooms (HABs) are known to cause fish deaths in the Gulf Of Mexico with a dinoflagellate called Karenia brevis a regular offender and the cause of “Red Tides.” However, early testing showed no evidence of poor water quality and by March this year, red tide toxins had not been detected in water samples.
They did find evidence of multiple other algae toxins however, and another dinoflagellate called Gambierdiscus, which produces a neurotoxin called ciguatoxin, the cause of ciguatera poisoning in some seafood, and known to produce diarrhea, vomiting, numbness, itchiness, sensitivity to hot and cold, dizziness, and weakness in humans.
Ciguatoxin wasn’t found in the sawfish’s muscles but was instead found in their gills and livers. Both the sawfish and the dinoflagellates are bottom-dwelling, putting the sawfish at higher risk of ingestion. They also found toxic levels in their prey.
In all, over eighty species of fish have been affected by the neurotoxin, including parrotfish, bull sharks, and goliath groupers. At least 54 sawfish have been confirmed dead to date including one they took in live and tried to rehabilitate. That’s from a population of just 650 breeding females in the whole of Florida. Pristis pectinata, the Smalltooth Sawfish has just two populations left – one in the Bahamas and one in Florida, and has been listed in the Endangered Species Act and CITES Appendix I – for species believed to be threatened with extinction.
Sawfish have been around for fifty million years, but the Anthropocene has not been kind to these curious cartilaginous fishes, with bycatch and habitat loss being the main cause of their steep decline. In normal circumstances, they can grow to 16 feet long and live for several decades.
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