Based on highest minimum counts of the manatee population in the United States, the Florida manatee (Trichechus manatus latirostris), found only in the southeastern U.S., constitutes the largest known group of West Indian manatees anywhere within the species' range (USFWS 2001). In contrast, the Antillean manatee (T. manatus manatus), which occurs in the Greater Antilles, eastern Mexico, Central America, north and northeastern South America and Trinidad (Lefebvre et al 2001) has a wider distribution area, but significantly smaller population sizes. It is suggested that Antillean manatees do not achieve larger population sizes because they are subject to poaching, incidental take in gillnets, and severe habitat loss in many areas within the range (USFWS 2001). Florida manatees are found only in the southeastern U.S., though a few have been documented in the Bahamas (Lefebvre et al 2001). When waters are warm, from approximately March - late November, some manatees travel along the east coast into Georgia, North and South Carolina, Virginia, and occasionally further north into New York and even Rhode Island (Deutsch et al. 2003). On Florida's west coast, some manatees move into Alabama, Mississippi, Louisiana and Texas during the spring and summer months (Powell and Rathbun 1984). During winter months (December - February), manatees are temperature-restricted to peninsular Florida, and their geographic range constricts to approximately the 20°C isotherm, including many warm-water refuge areas around artesian springs, power plants, and other industrial sites where thermal effluents occur. Natural refuges include Blue Spring, Crystal River, Homasassa Spring, and Warm Mineral Spring. Ten major thermal refuges around power plants have also been identified, 3 on the west coast, and 7 on the east coast (Reynolds and Wilcox 1986, 1994). The northern extent of the Florida manatee was believed to be south Florida; however, loss of habitat in south Florida, coupled with expansion of human population with consequent construction of power plants and other industrial sites that discharge warm effluents, have caused manatees to expand their wintering grounds into previously unsuitable areas.The historical ranges of T. m. latirostris and T. m. manatus may overlap along the Gulf coast of Texas where strays from Mexico and Florida sometimes co-occur (USFWS 2001). Manatees are distributed throughout the India River Lagoon. Historical accounts of manatee occurrence and movement suggest that manatees are likely to be as geographically widespread as they are at present, but are less abundant in many regions (USFWS 2001; Lefebvre et al. 2001), including the India River Lagoon.
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