Florida Manatee (Trichechus manatus latirostris) is one of the most threatened marine mammals in the coastal areas of the United States. Their populations had been dramatically declining due to various anthropogenicfactors. Causes of manatee deaths can be broken down into five categories: watercrafts, crushed/drown by flood gate or canal lock, entanglement, perinatal, and other natural factors (such as disease and natural catastrophe). Unfortunately, three among these five categories are associated with human. Hence, we aimed to estimate and compare anthropogenic and natural catastrophiceffects on the manatee population dynamics. We conducted a literature review to obtain the basic demographic data and then developed a stage-structure population dynamics model of Florida manatee. Moreover, we used the new data from Florida Fish and Wildlife Conservation Commission synoptic surveys to calculate average mortality rates and 95% confidence interval of those for five scenarios including baseline, anthropogenic threats, cold stress, 2010 oil spills, and perinatal effects. We simulated each scenario with the worst, average, and better effects from each of their average mortality rates. Finally, the model ran for 30 years with an initial population of 2000 and carrying capacity of 5000, which projected the Florida Manatee population with the effects of each mortality scenario.
Results/Conclusions
Our preliminary results showed that the leading factors affecting the manatee population were natural causes followed by the cold stress, the oil spill, and anthropogenic threats. Even though the Florida manatee did not display signs of extinction by each individual scenario, it showed extinction with the combined mortality rates. Our results suggested it is important to protect the species and monitor for anthropogenic effects on the species.