West Indian Manatee (Trichechus manatus) 5-Year Review: Summary and Evaluation

摘要

Recovery efforts for the Florida manatee are highly complex, given the tremendous amount of controversy and conflict associated with ensuring the persistence of this species. Increasing human population growth and related development in Florida, increases in recreational boating activity, and anticipated changes in the network of warm water sources pose significant challenges. Current recovery criteria for the Florida manatee are flawed and need to be updated based on the definitions in the ESA and significant recent improvements in science allowing the Service to better assess and quantify threats on the viability of the subspecies. Florida manatees are exhibiting positive population growth rates on the Atlantic Coast, in the upper St Johns River, and in the Northwest regions of peninsular Florida. Manatee populations in southwest Florida may be slightly declining though statistical confidence intervals are broad. The minimum estimate of the statewide population is approximately 3,300 animals. The threats analysis indicates that the most significant threats to Florida manatees are collisions with boats and potential loss of warm water habitat throughout the state. In southwest Florida, red tide in combination with other threats such as watercraft collisions and the potential loss of warm water sites results in negative synergistic effects to population size in this part of the state. Broad regulatory frameworks exist at both the federal and state levels to address the watercraft threat. Extensive on-the-water regulatory measures are in place to minimize the potential for collisions with boats. However, these measures are not sufficiently effective to prevent a decline of manatees in southwest Florida because of the combined effect of other threats (i.e., red tide). Efforts to protect and ensure the long term availability of warm water sources have been initiated but measures are not in place. Failure to protect existing sources or to provide secure surrogate habitats for the long-term could lead to a future decline in the Florida manatee population, reduced long term carrying capacity, and an elevated risk of extinction on either coast of Florida.