M. Marmontel et al., POPULATION VIABILITY ANALYSIS OF THE FLORIDA MANATEE (TRICHECHUS-MANATUS LATIROSTRIS), 1976-1991, Conservation biology, 11(2), 1997, pp. 467-481
Recent development of age-determination techniques for Florida manatee
s (Trichechus manatus latirostris) has permitted derivation of age-spe
cific data on reproduction and survival of a sample of 1212 carcasses
obtained throughout Florida from 1976-1991. Population viability analy
sis using these data projects a slightly negative growth rate (-0.003)
and an unacceptably low probability of persistence (0.44) over 1000 y
ears. The main factors affecting population projections were adult sur
vival and fecundity. A 10% increase in adult mortality would drive the
population to extinction over a 1000-year time scale, whereas a 10% d
ecrease in adult mortality would allow slow population growth. A 10% d
ecrease in reproduction would also result in extinction. We conclude t
hat management must focus on retaining and improving the conditions un
der which manatee demography operates. The major identified agent of m
ortality is boat-manatee collisions, and rapidly increasing numbers of
humans and registered boats portend an increase in manatee mortality.
Zoning of manatee-occupied wafers for reductions in boating activity
and speed is essential to safeguard the manatee population. If boating
regulations being implemented by the state of Florida in each of 13 k
ey coastal counties are completed, enforced, and effective, manatees a
nd human recreation could coexist indefinitely. If regulation is unsuc
cessful, the Florida manatee population a likely to decline slowly tow
ard extinction.