The Florida manatee has long been subjected to human (eg. watercraft) and environmental (eg. red-tide) threats, the former resulting in legislation and the implementation of watercraft speed limits. Whether this has had an impact on Florida manatee populations and their causes of death since 1995 was examined using data obtained from the Florida Fish and Wildlife Conservation Commission.

Data pertaining to causes of death, synoptic survey data, and annual numbers of carcasses was charted over the period from 1995-2004. Interestingly, periodic spikes in various causes of Florida manatee deaths occur which can be at least partially attributed to climactic effects. Flood gate/canal lock deaths decreased significantly such that only 1% of deaths are now attributable to this.

The proportion of deaths attributed to watercraft increased 4%. When comparing years with similar death totals, 272 in 2000 and 276 in 2004, the absolute and percentage values of watercraft-related incidents actually decreased. The contribution of cold stress mortality has increased by 18% and showed a more than 50-fold increase in absolute numbers. Perinatal deaths increased in absolute values almost 50%.

Synoptic surveys showed significant yearly variability in population counts –overall however no significant changes in population are occurring. These population figures are limited by the technique which cannot control for events that might alter manatee locations at the time of the survey.

From these results, it is clear that Florida manatee are still facing both human and environmental stressors whose relative impact has changed over time. Watercraft-related mortalities have recently been replaced by perinatal mortality followed closed by a significant rise in cold stress-related deaths. Further research should focus on the specific causes of perinatal deaths and cold stress if we are to significantly and favorably impact on Florida manatee conservation.

Presented as a poster at the XXth Annual SMM Conference