How has the population of the amazonian manatee changed over time?

Although the population size and distribution of Amazonian manatees are not highly documented, I found the following information that may be of assistance to you. In 1981 it was estimated that 15000-9000 individuals existed. In 2006 it was suggested that less than 10000 individuals existed in the world. In Cape Ivory, it was estimated that less than 750 animals existed in the mid 1980's, and in 2000 the population was estimated to be between 750-800 animals, showing a stable population size on Cape Ivory. A 2001 census in Senegal suggested that manatees in this area were seriously declining and almost to the point of extinction.