Manatees vs. Man and the Caloosahatchie River
I''m not sure where you''re getting your information from, the Florida manatee is a native species, they have never been imported.
Pre-historic Florida Indians created ceremonial pipes in the shapes of manatees.
The first laws protecting manatees where enacted in 1893, before that, they had been netted and shot by Indians for food and then later shot and killed by "pioneers" for meat and oil.
The Florida manatee in actually a subspecies of the West Indian manatee and it''s found only on the East and Gulf coasts.
I lived in Florida for a few years and became interested in them, their history and the conservation efforts.
That site has some interesting facts and information regarding manatees.