The West Indian manatee, Trichechus manatus, is a distinct species of manatee that is found in the warm coastal waters and rivers of Florida (Lefebvre et al. 2001). Globally the West Indian manatee is listed as vulnerable by the International Union for Conservation of Nature (2014). The populations of West Indian manatees that call Florida’s waters home are not doing as well. The U.S. Fish and Wildlife Service and the Florida Fish and Wildlife Conservation Commission (FFWCC) list the West Indian manatee as endangered (2014).
The predominate cause of declines in Florida’s manatee populations are considered to be anthropogenic. Anthropogenic activities strongly influence manatee behavior and food sources (FFWCC 2007). Manatees have a relatively slow life history manatees calve approximately every three years, gestation is eleven to thirteen months and sexual maturity is reached between four and seven years old (FFWCC 2007). Calves are dependent upon their mothers for at least the first two years of life and Manatees life expectancy is approximately 60 years old (FFWCC 2007). The primary threats that manatees face from anthropogenic influences include entanglement, habitat loss, and watercraft collisions.
Manatees can become entangled in traps and fishing gears that can cause drowning and scarring (FFWCC 2007). Entanglement may also lead to crushing by watercraft, canal locks, or other structures (FFWCC 2007). Manatees can also drown because manatees may become trapped in or by structures and pipes used for water control devices. Debris from fisheries operations or pollution can be accidentally ingested and this is very harmful for manatees.
Manatees are a highly migratory species, location changes throughout the year based on preferred water temperature (Weigle et al. 2001; Deutsch et al. 2003). When the water cools in the fall and winter Manatees will gather around warm water refuges (FFWCC 2007). Sometimes these refuges are natural sources such as inlets typically though they are artificial, having been created by the outfalls of coastal power plants. Southern Florida is well known for large gatherings of Manatees in the winter, this provides a popular tourist attraction.
Manatees are dependent on these warm water areas for survival; this is why they are found in large groups (Reynolds and Wilcox 1994; USFWS 2001). These areas provide a warm refuge between feeding periods in sea grass beds. The predicted decline in these warm water refuges in the coming decades will be a serious threat to manatee population stability (Runge et al. 2007). Maintaining and protecting these refuges will be essential for manatee management efforts. Thermal plumes generated by power plants provide a much needed source of warm-water in winter conditions. Unfortunately these crucial areas are being lost to technological improvements that are more energy efficient and produce less heat.
One of the...