Chapter III — Species of Special Concern 
Known manatee mortality in the southeastern United States (excluding Puerto Rico) reported 
through the manatee salvage and necropsy program from 1978-1992' 
Table 2. 
Flood 
Vessel- Gate and 
Related Perinatal Lock 
Deaths Deaths Deaths 
Year No. (% No. (% No. (% 
1978 21 (24) 10 (12) 9 (10) 
1979 24 (28) 9 (12) 8 (10) 
1980 16 (23) 13 (19) 8 (12) 
1981 25 (21) 13 (11) 2 (2) 
1982 20 (17) 14 (12) 3 (3) 
1983 15 (19) 18 (22) 7 (9) 
1984 34 (26) 26 (20) 3 (2) 
1985 35 (27) 25 (20) 3 (2) 
1986 33 (26) 27 (22) 3 (2) 
1987 39 (33) 30 (25) 5 (4) 
1988 43 (32) 30 (22) 7 (5) 
1989 51 (29) 37 (21) 3 (2) 
1990 49 (23) 45 (21) 3 (1) 
1991 53 (30) 53 (30) 9 (5) 
1992 38 (23) 49 (30) 5 (3) 
Other Deaths Deaths Total 
Deaths Inside Outside Deaths in 
No. (% Florida Florida S.E. U.S. 
46 (53) 86 0 86 
37 (47) 77 1 78 
30 (45) 63 4 67 
79 (66) 116 3 119 
83 (69) 114 6 120 
41 (51) 81 0 81 
68 (52) 128 3 131 
66 (51) 120 9 129 
62 (50) 122 3 125 
44 (37) 114 4 118 
54 (40) 133 1 134 
83 (48) 166 8 174 
117 (55) 206 8 214 
60 (34) 174 1 175 
73 (44) 162 4 166 
1 Totals provided by the Florida Department of Natural Resources for 1992 are preliminary. 
stillborn and newborn calf) deaths. These two causes 
accounted for 36 percent of all known deaths between 
1978 to 1983. Between 1988 and 1992, the two 
categories combined increased to 52 percent of the 
total mortality. 
Vessel-related manatee deaths have reached record 
levels in six of the past nine years. Between 1978 and 
1983, 22 percent of the total known manatee mortality 
was attributed to this cause. Between 1988 and 1991 
it was responsible for 28 percent of the total mortali- 
ty. These percentages are probably underestimated 
because some carcasses are so badly decomposed by 
the time they are recovered that the cause of death is 
no longer detectable. As a result, some vessel-related 
deaths probably are classified as “undetermined.” 
Increasing vessel-related manatee deaths parallel a 
dramatic increase in vessel traffic and vessel numbers. 
For example, in 1960 the number of boats registered 
in Florida was about 100,000; in 1991, the most 
recent year for which data have been tabulated, this 
number exceeded 700,000. In 1992 there was a 
marked decline in vessel-related deaths. While this 
may reflect increased efforts to regulate boat speeds in 
manatee habitat, data are not yet sufficient to evaluate 
cause-and-effect relationships between vessel-related 
manatee mortality and regulatory measures. 
Perinatal deaths show a much sharper increase. 
Records have been equaled or exceeded in seven of 
the past nine years. From 1978 to 1983 about 14 
percent of the total known mortality was listed as 
perinatal; between 1988 and 1992 it accounted for 25 
percent. The cause of this increase is uncertain and 
may be due to different factors in different areas. 
Possible causes include pollution, disease, infection, 
poor nutrition, environmental changes, changes in the 
population age structure (i.e., an increasing percent- 
age of very young mothers), increasing noise, distur- 
bance or stress from vessel traffic, collisions between 
vessels and nursing females, or a combination of these 
and other factors. 
