He said researchers believe 60 manatee deaths last year were related to red tide.
Rose said the main factor in manatee deaths varies from year to year. In 2013, red tide was the main cause, and in 2010, it was cold weather.
Statewide, 106 manatee deaths were attributed to watercraft collisions, according to numbers from the FWC. Kerr said watercraft collisions account for about 20 percent of manatee deaths over the past five years.
The Associated Press contributed to this report.