Thermal refuges are important for the endangered Florida manatee (Trichechu
s manatus latirostris) during winter cold periods in temperate latitudes. H
owever, little research has examined impacts on manatees from human disturb
ance during these critical periods. We studied the effect of recreational b
oating activity on manatee use of established sanctuaries in the natural th
ermal refuge created by warm-water springs in Kings Bay, Crystal River, Flo
rida. 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 u
se 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, w
ith significantly greater numbers of boats in the study area on weekends ((
x) over bar=32.7, SE=2.71) than on weekdays ((x) over bar=10.7, SE=1.23). W
e concluded that recreational boating influenced manatee distribution, sanc
tuaries are important to manatees in Kings Bay, and sanctuaries are an effe
ctive management tool to reduce the impact of boating activities on manatee
s.