Scientists have a potential lead for what is causing bizarre spinning fish deaths in Florida

Nearly 500 deaths have been observed in the mysterious cases, officials said.
Smalltooth sawfish NOAA
Posted at 8:53 AM, May 13, 2024

Scientists may have identified a prime suspect in what is causing abnormal behavior and deaths in endangered smalltooth sawfish in the Florida Keys.

The bizarre, fatal, fish-spinning events were first observed last fall, prompting state and federal agencies to launch an investigation. According to the Florida Fish and Wildlife Conservation Commission (FWC), there have been nearly 500 incident reports to its fish kill hotline as of May 8.

A smalltooth sawfish is shown.

Animals and Insects

Fish are spinning and dying in Florida, and scientists don't know why

Alex Arger
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Dozens of species have been impacted, according to the commission. However, scientists are most concerned about the impacts on the vulnerable smalltooth sawfish population, which is classified as critically endangered.

As of May 8, the FWC said 47 smalltooth sawfish deaths have been reported, but scientists believe the actual number is higher. There is limited data on how many of these rays remain in the wild.

The FWC said there are no apparent signs of a communicable pathogen to blame for the spinning fish deaths and it has ruled out red tide, dissolved oxygen, salinity, pH and water temperature as a cause.

Most results from the hundreds of fish tissue and water tests came back normal, but harmful algal species were found in some of the samples. The FWC said more work is needed to determine if this could be the culprit.

In the meantime, the FWC said reporting fish kill incidents is essential in helping it conduct more research.

The Mote Marine Laboratory team in Sarasota, Florida, attempted to save the life of a distressed sawfish that was seen whirling in the Cudjoe Bay in the Florida Keys at the beginning of April. The scientists were able to take the sawfish to its rehabilitation center, but the efforts to improve the animal's condition were unsuccessful.

A necropsy will be performed on the sawfish that will potentially determine its cause of death. Officials with Mote said a joint effort of this kind to save a sawfish had never been attempted before.

Sawfish are named for their unique long snout that is lined with teeth, resembling a saw. The smalltooth is one of five species of the shark-like ray group that inhabits tropical waters. The decline in the number of sawfish is blamed on habitat loss due to shoreline development and mortality from fishing.