The latest figures from the Florida Fish and Wildlife Commission show that as of October 15, 974 manatees have been found dead, more than twice the number that died all of last year and more than any other year on record.
The number represents more than 10% of the total population of manatees in the state.
Officials fear the onset of winter and colder weather could bring another wave of deaths.
Environmental officials say there is no real mystery for the die-off. They say over the past 10 years, seagrass, the primary food for the animals, has been steadily declining.
When wildlife officials conducted postmortem examinations on the bodies found in the first half of the year, the vast majority were found to have starved to death.
Environmental experts say the seagrass is being killed off by declining water quality traced to man-made sources such as fertilizer runoff, wastewater discharges and other pollutants. State estimates show that since 2009, about 58% of the seagrass has been lost in the Indian River Lagoon, a prime habitat for manatees, The Associated Press reported.
The Florida Legislature this year approved $8 million in funding for a manatee habitat restoration program run by state and federal environmental officials.
The Associated Press reports the Fish and Wildlife Commission is calling for state lawmakers to approve another $7 million for seagrass restoration projects, manatee rehabilitation centers and other projects.
The manatees in Florida are West Indian animals known for their round bodies, large front flippers and paddle-shaped, flat tails. The average adult is just more than 3 meters long, weighs as much as 550 kilograms and may live as long as 65 years. They are closely related to elephants.
Some information in this report came from The Associated Press.