Manatee impacts from the 2022-2023 red tide bloom
Updated May 17, 2023
Manatee mortality from the present red tide bloom was first documented in November 2022. Numbers of verified carcasses in the bloom were elevated in the southwest region during March 2023 when 86 carcasses (2023 preliminary manatee mortality table) were verified in this region (Pinellas, Hillsborough, Manatee, Charlotte, Lee, and Collier counties). Clusters of carcass locations were documented in Pinellas and Lee counties. Currently, the red tide table only lists carcasses that were fully necropsied; however, select carcasses that did not receive a full necropsy (death code Verified; Not Necropsied) will be included in this table at a later time once all data from this red tide bloom can be reviewed. The leading cause of death among necropsied carcasses in the southwest region during spring was red tide-related. Similarly, the total carcass numbers documented in the bloom follow the pattern of previous manatee spring red tide events in southwest Florida.
Between February 24 and May 6, ten manatees with signs of brevetoxicosis (see below) were rescued and are currently in rehabilitation.
Brevetoxin is a neurotoxin that can weaken or paralyze a manatee or cause seizures. Necropsy findings include lung edema from drowning or toxic shock. Signs of brevetoxicosis in live manatees include struggling to surface and breathe, seizures, facial tremors, abnormal position in the water (belly up, vertical position head or tail down), weakness, or beaching in shallow water. Manatee exposure to red tide is mostly through ingestion of brevetoxin accumulated in seagrass. Even after red tide dissipates seagrasses can still retain brevetoxins for 1-2 months after a bloom. Mass mortality from red tide typically occurs in the spring, when a red tide bloom coincides with manatee migration away from warm-water sites.
Please report any manatees in distress or carcasses to FWC’s Wildlife Alert Hotline (1-888-404-3922).