Thermal refuges are important for the endangered Florida manatee (Trichechus manatus latirostris) during winter cold periods in temperate latitudes. However, little research has examined impacts on manatees from human disturbance during these critical periods. We studied the effect of recreational boating activity on manatee use of established sanctuaries in the natural thermal refuge created by warm-water springs in Kings Bay, Crystal River, Florida. We examined the relationship among manatee use of the study area and sanctuaries, temperature, and level of boating activity. Manatees continued to use the Bay regardless of the number of boats present; however, their use of sanctuaries in the southern portion of the Bay increased (P<0.001) as number of boats increased. Temperature, as expected, was inversely related to manatee use of the study area. Human activity patterns were variable, with significantly greater numbers of boats in the study area on weekends (x??=32.7, SE=2.71) than on weekdays (x??=10.7, SE=1.23). We concluded that recreational boating influenced manatee distribution, sanctuaries are important to manatees in Kings Bay, and sanctuaries are an effective management tool to reduce the impact of boating activities on manatees.
