The Florida Fish and Wildlife Conservation Commission has ruled out a slew of potential issues contributing to bizarre fish behavior believed to be connected with a rise in fish deaths, though more testing is needed to determine a cause.
Fish began exhibiting a strange "spinning" behavior in the Florida Keys last fall, the FWC said in a recent update. In the months since, almost 500 Fish Kill Hotline reports have been made to the FWC, and officials are growing increasingly concerned about the effects on the smalltooth sawfish, a type of endangered ray. Sawfish mortalities were first reported in January, the FWC said, and at least 47 sawfish have died. So far, officials have collected more than 300 fish samples and more than 200 water samples. Testing has not determined a cause of the strange behavior and widespread deaths, but it has eliminated several possible culprits.
"Right now, we are only primarily seeing mortality in smalltooth sawfish, which is especially concerning because they are an endangered species," an FWC spokesperson told Newsweek. "However, we were receiving reports of spinning fish for more than 50 species."
On May 8, the FWC issued an update saying officials had a clearer picture of the area's water quality. After conducting tests, officials have ruled that oxygen levels, salinity, pH and water temperature are not at fault for the strange fish behavior or deaths. Officials also tested for more than 250 chemicals. Results showed that the chemicals were either not detected or were below biological thresholds. The results of a heavy metal test are still pending.
Officials also conducted fish necropsies, or animal autopsies, and learned that disease or bacterial infection were not at fault either. Red tide, a type of harmful algal bloom, was also ruled out. However, the FWC learned that there were high levels of Gambierdiscus spp., a different type of harmful algal bloom, present in the area.
Not all algae are toxic, but it's impossible to tell which are by looking at them. Harmful algal blooms can prompt officials to close lakes to prevent exposure, as the algae can be toxic to people and their pets. The blooms can last for months, depending on the conditions.
"Other harmful algal species have been observed in benthic and water samples examined by FWC and Florida Gulf Coast University (FGCU)," the FWC update said. "Associated toxins have been detected in water and benthic samples, and fish tissues, by the University of South Alabama, but more work is needed to determine if this is the cause of the unusual behavior."
Gambierdiscus spp. can produce ciguatoxins, which can have a widespread effect on public health, such as causing foodborne illness. However, the levels were lower when samples were taken in March.
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Scientists Close In on Potential Cause of Florida Fish Spinning to Death - Newsweek
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