Biologists with the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute documented 429 manatee carcasses in state waters in 2009.
Of those, 97 were watercraft-related deaths, the biologists said. The preliminary data indicate the numbers for that category were at a record high for a calendar year.
Biologists also documented a record high of 56 cold stress-related deaths in 2009, which was more than double the five-year average and 114 newborn deaths.
"Given the high count of manatees from 2009 aerial surveys, it might be perceived that the high number of deaths is simply because of a larger manatee population. The situation is not that simple," the FWC said in a release.
"Both the carcass totals and the annual counts from statewide aerial surveys are considered minimum numbers only, and they cannot be used to calculate long-term population trends," the release continues. "However, models used by the FWC to assess the status of the species indicate the manatee population is stable or increasing in most areas of the state in the near term."
To maintain the species into the future, the FWC says it will continue to monitor threats such as watercraft strikes and loss of warm-water habitat, which models indicate can profoundly affect the manatee population.