About 30 dead fish have been observed in the C-24 Canal in Port St. Lucie as state and local officials investigate what may have caused the fish kill.
The Florida Fish and Wildlife Conservation Commission has received three reports of a fish kill in the canal and has been coordinating with local and state agencies to investigate.
The city of Port St. Lucie and the South Florida Water Management District spent about six hours investigating the area and observed dead fish representing multiple species, according to FWC. Investigators found low dissolved oxygen levels in the canal, while water color and turbidity appeared normal.
Investigators did not observe visible algal growth or evidence of an illicit discharge, FWC said.
The South Florida Water Management District said its staff investigated the C-24 Canal upstream from the S-49 water control structure after receiving reports from the city.
“District staff visited the site and did observe some dead fish,” a South Florida Water Management District spokesperson said. The findings were reported to FWC.
The Florida Department of Environmental Protection is scheduled to collect water samples from the area and send them to FWC for analysis.
FWC said low dissolved oxygen may have contributed to the fish kill based on observations so far. Dissolved oxygen is essential for fish and other aquatic life, and fish can become stressed, suffocate and die when oxygen concentrations fall too low.
One sign of low dissolved oxygen is fish gasping at the surface. In one report received by FWC, a member of the public reported seeing fish gasping at the surface.
FWC said low dissolved oxygen can have several causes, including high water temperatures, storms and heavy rainfall, drought, algal blooms and extended periods of cloudy weather.
According to FWC's fish kill information, high temperatures can be particularly relevant during Florida's summer months. Fish kills caused by high temperatures occur most often in July and August, according to the agency. Warmer water also holds less oxygen, which can make it more difficult for fish to breathe.
FWC also notes that algae and aquatic plants produce oxygen during daylight through photosynthesis but consume oxygen at night. In warm, stagnant water, oxygen levels can become low enough, particularly by early morning, to cause fish to suffocate.
The agency said algae blooms can also contribute to low dissolved oxygen when algae die and decompose, consuming oxygen in the water. However, investigators did not observe visible algal growth during their examination of the C-24 Canal.
The South Florida Water Management District said it has no other reports of fish kills at this time.
FWC encourages members of the public who observe abnormal fish behavior, signs of fish disease or fish kills to report their observations through its Fish Kill Hotline at 1-800-636-0511 or through the agency's online reporting form.