Scientists and researchers are baffled by a string of fish deaths occurring in South Florida, including an endangered species native to the region. The Florida Fish and Wildlife Commission (FWC) has classified the event as an "abnormal fish behavior event," as hundreds of fish are washing up dead on the shores of the Florida Keys.

The peculiar behavior of these fish has caught the attention of experts, with fish spinning in circles and floating upside down. Investigations conducted by the FWC, in collaboration with the Florida Department of Environmental Protection and other agencies, have ruled out common causes like dissolved oxygen levels, salinity, pH, temperature, and red tide toxins. Water samples have shown no trace of harmful substances, pollutants, or neurotoxins either.

Professor Mike Parsons, from the Water School at Florida Gulf Coast University, revealed that the affected fish stopped their erratic behavior when placed in "clean" water, suggesting a potential connection to some form of harmful algal bloom or neurotoxin. However, pinpointing the exact cause amidst the vast array of possible factors has proven to be a challenge for researchers.

Of significant concern are the critically endangered smalltooth sawfish, a species heavily impacted by these fish deaths. The National Oceanic and Atmospheric Administration (NOAA) Fisheries has launched an emergency response effort to rescue sick sawfish, an unprecedented endeavor. To investigate further, the FWC has sent fish samples, including 12 smalltooth sawfish, to the University of South Alabama for analysis. While additional tissues are being processed, researchers remain cautious about speculating on the cause behind the unusual behavior.

The number of sawfish mortalities has reached 28, with over 265 reports of fish deaths received by the FWC. Most of the sawfish mortalities have occurred in the lower Florida Keys, but reports indicate similar symptoms outside of the Keys, including near Everglades National Park.

As the investigation continues, health officials are advising residents to avoid consuming any fish displaying spinning behavior or caught in areas with reported spinning fish. The exact population of smalltooth sawfish remains unknown, but their historical range from North Carolina to Texas has been greatly reduced, primarily due to bycatch in fisheries and habitat loss caused by coastal development.

The smalltooth sawfish, the first marine fish to receive protection under the Endangered Species Act in 2003, faces additional challenges due to a limited number of breeding females. Alarmed by the situation, Adam Brame, NOAA Fisheries' sawfish recovery coordinator, stressed the significance of public participation. He urged individuals who witness any abnormal fish behavior to report it to the hotline at 1-844-4SAWFISH (1-844-472-9347) or via email at Sawfish@myfwc.com.

As the mysterious fish deaths persist, scientists and researchers remain committed to unraveling the cause behind this perplexing event, serving not only to protect the endangered species but also to preserve the delicate marine ecosystems of South Florida.