PORT ST. LUCIE — State and city officials are investigating a large fish kill at Sawgrass Lakes, a Port St. Lucie residential community, after more than 1,500 dead fish were removed last week.
The Florida Fish and Wildlife Conservation Commission (FWC) first received reports on Aug. 13, with seven reports filed to date — three from residents and four from city staff, Jonathon Veach, an FWC information specialist, said in an email statement.
“City staff documented the removal of 1,527 fish. Most were tilapia, along with smaller numbers of bluegill, catfish, bass, and bream,” Veach said. “While this reflects the number of fish removed, it is not possible to determine the exact number of fish lost during a fish kill event.”
At this stage, low dissolved oxygen (DO) levels are considered the most likely cause, Veach said, adding that summer heat, algae growth, and other environmental factors may have contributed. “The last significant fish kill of this scale reported in St. Lucie County occurred in June 2020 in the C-24 Canal,” he said.
FWC analyzed a city-collected water sample and found it consisted mostly of cyanobacteria and dinoflagellates, Veach said.
“It is possible that the algae, summer temperatures, and other factors are contributing to low DO,” he said.
According to FWC guidance, fish kills are most often linked to drops in dissolved oxygen, especially during the hot summer months when warm water holds less oxygen.
Scott Samples, the city’s strategic communications manager, said in an email statement that Port St. Lucie officials were notified on Aug. 14 and “immediately responded and are investigating for a potential cause.”
“Oxygen levels were tested, and the results were normal,” Samples said. He added that “Port St. Lucie Utility Systems also confirmed that no reclaimed water, wastewater or chemicals have been released into this body of water” near the Westport Wastewater Treatment Facility.
The city has not sprayed herbicides in the area since 2022, Samples said.
Samples said the city collected several water quality tests and sent them to a lab, reached out to state environmental agencies, and submitted fish samples to the Bronson Animal Disease Diagnostic Laboratory. Results are expected as early as this week.
“As we continue to investigate potential causes, we are considering environmental factors as well, including the impact sustained high summer temperatures can have on fish,” Samples said. “We have heard from FWC staff that similar mass fish deaths have happened in other areas of South Florida this summer.”
The city has been in contact with Sawgrass Lakes residents since the incident, he said.
FWC encouraged the public to report fish kills, diseased fish, or fish displaying abnormal behavior to its Fish Kill Hotline at 800-636-0511 or online at MyFWC.com/FishKill.