Red Tide & Fish Kill Resources


Red tide is when certain types of microscopic plant-like organisms called alga "bloom" in high concentrations. Karenia brevis, the alga that causes most cases of red tide in Florida, produces a toxin that can affect the central nervous system of fish and other forms of marine life. In high enough concentrations, this algae bloom often turns the water a distinct color.

Red tides have been documented along Florida's gulf coast since the 1840s and probably occurred much earlier. In fact, Fish kills around Tampa Bay were mentioned in the logs of Spanish explorers. Due to the numerous factors associated with red tides, otherwise known as "harmful algal blooms" (such as winds, currents, & water temperature), it is difficult to predict the intensity and impacts of red tides along our coasts.

Human Health

No deaths of humans have been attributed to red tide, but people may experience respiratory irritation (coughing, sneezing, and tearing) when the red tide organism (Karenia brevis) is present along a coast and winds blow its toxic aerosol onshore. Swimming is usually safe, but skin irritation and burning is possible in areas of high concentration of red tide.

Seafood Safety

Shellfish (clams & oysters) should NOT be consumed in areas where red tide is present because cooking does not destroy the red tide toxin. But shrimp, crabs and fish can be eaten during a red tide because the toxin is not absorbed in the edible tissues of these animals (scallops can be consumed, but ONLY the muscle and NOT the whole animal). However, if a red tide is in the area, eating distressed or dead animals is discouraged because the reason for the animal’s strange behavior or death cannot be absolutely known. It could be something unrelated to red tide.

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