2023 Manatee Mortality Data
Fish and Wildlife Research Institute staff examine an adult male carcass at the Marine Mammal Pathobiology Lab in Saint Petersburg, FL. Necropsy determined that the manatee died from injuries caused by propeller cuts.
The total statewide manatee mortality number (556) for 2023 was well below the 5-year average (793) of the most recent years and at its lowest since 2017 when 538 carcasses were recorded.
The leading causes of death were watercraft-related and natural disease. Only a portion of all carcasses was fully necropsied, so there were likely more of these causes in the carcasses that are listed in the ‘Verified; Not Necropsied’ category, especially on the Gulf coast where a stratified random sampling approach was used in 2023. Approximately 20% of the total statewide mortality in 2023 was attributed to a significant red tide bloom in southwest Florida earlier in the year. Population models identify both watercraft collisions and red tide blooms as one of the most significant threats to manatees long-term. In contrast with the Gulf coast, a high proportion (81%) of Atlantic coast carcasses was fully necropsied for the ongoing health investigation in the Unusual Mortality Event from starvation, but starvation-related mortality was very low (3% of Atlantic coast carcasses) in 2023.
Researchers documented ten manatees that died from entrapment and drowning in culverts, which fall under the ‘Other Human’ cause of death category. All cases were in Brevard County and involved four separate draining pipes. A group of five manatees was found in one of these, and one pair in another. Manatees may follow each other into the culvert, but if they cannot exit on the other end and cannot turn around, they will drown if the structure is fully submerged. FWC and USFWS continuously work with owners of culverts that are identified as manatee drowning hazards to install exclusion devices. Three out of these four culverts have been closed off since the mortalities were documented in 2023, and the last one which was identified as a hazard in mid-December is in the process of being closed off from manatee access.
No mortalities were definitively attributed to Hurricane Idalia, but FWC staff and partners rescued ten manatees across southwest Florida that had become entrapped after storms floods receded.