Manatees at David A Straz Jr Manatee Critical Care Center in ZooTampa at Lowry Park in Tampa, Florida.

Red tides caused by human use of fertilizers, loss of food in their natural habitat and collision with boats are main causes of manatee deaths.

According to the Florida Wildlife Service, 674 manatees were found dead in Florida waters from January 1 to April 16 this year, nearly triple of corresponding period for each of the past five years.