Chapter n 



SPECIES OF SPECIAL CONCERN 



Section 202 of the Marine Mammal Protection Act 

 directs the Marine Mammal Commission, in consulta- 

 tion with its Committee of Scientific Advisors on 

 Marine Mammals, to make recommendations to the 

 Departments of Commerce and the Interior and other 

 agencies on actions needed to protect and conserve 

 marine mammals. In 1991, the Commission contin- 

 ued to devote special attention to marine mammals 

 listed as endangered or threatened under the Endan- 

 gered Species Act (Table 1). 



Because of their occurrence in U.S. waters and/or 

 an exceedingly high risk of extinction, greatest effort 

 in 1991 was devoted to West Indian manatees, Hawai- 

 ian monk seals, Steller sea lions, California sea otters, 

 northern right whales, humpback whales, bowhead 

 whales, gray whales, and Gulf of California harbor 

 porpoises. Given the serious threats facing certain 

 other species in U.S. waters, special attention also 

 was given to North Pacific fur seals. Pacific walruses, 

 sea otters and harbor seals in Alaska, polar bears, 

 killer whales, harbor porpoises, and bottlenose dol- 

 phins. Efforts to protect these species are described 

 in this Chapter. 



West Indian Manatee 

 (Trichechus manatus) 



One of the most endangered marine manunals in 

 U.S. waters is the West Indian manatee. The species' 

 U.S. range is limited primarily to rivers and coastal 

 waters of peninsular Florida and southern Georgia. 

 The southeastern U.S. population, also called the 

 Florida manatee population, is geographically isolated 

 from other manatee populations and is recognized as 

 a separate sub-species (7. manatus latirostris). Colli- 

 sions with boats and habitat destruction are by far the 

 leading human threats to these animals. 



Early in 1991, the Florida Department of Natural 

 Resources organized two state-wide aerial surveys to 

 count manatees in Florida. They yielded preliminary 

 counts of 1,268 and 1,465 animals. Although the 

 counts closely match the previous minimum popula- 

 tion estimate (1,200 animals), which was based 

 primarily on counts at warm-water refuges, weather 

 conditions in all areas were not optimal. Because 

 comparable aerial surveys were not conducted before 

 1991 and because the previous estimate was intended 

 only as a conservative best guess of minimum popula- 

 tion size, the surveys are not comparable to any 

 earlier estimates. The recent counts are, however, the 

 largest ever recorded anywhere in the species' range. 



Outside of the United States, West Indian manatees 

 are found in the Greater Antilles (including Puerto 

 Rico), along the Atlantic coast of Central America and 

 northern South America, and in Trinidad and Tobago. 

 In these areas, manatees are considered members of a 

 second subspecies, the Antillean manatee {T. manatus 

 manatus). These populations are thought to be small, 

 numbering perhaps 100 or fewer in most countries, 

 and generally declining. Major threats include poach- 

 ing, incidental take in gillnets, and habitat degrada- 

 tion. Since effective conservation programs do not 

 exist in most other countries, the species' long-term 

 survival may well depend on the success of efforts to 

 protect remaining animals in Florida and Georgia. 



Mortality in the southeastern United States, how- 

 ever, has increased steadily since 1980 (Table 2). 

 Recent levels are especially alarming given what is 

 known about the species' abundance and low repro- 

 ductive rate. The high 1990 mortality was caused, in 

 part, by the death of at least 47 animals following an 

 intense cold spell the last week of 1989. However, 

 most of the steady increase over the past 13 years is 

 attributable to increasing numbers of vessel-related 

 deaths and perinatal calf mortality. 



