It's not easy to find out, but once or twice a year a statewide aerial survey is conducted, weather permitting, throughout Florida by a team of biologists.
Several agencies work together to conduct the count.
The Florida Department of Environmental Protection at the Florida Marine Research Institute in St. Petersburg coordinates the survey and tabulates the results. Normally, this occurs over a two day period following the passage of a cold front. During January or February major cold fronts bring clear air and low water temperatures, which causes the manatees to gather in warm water sites. Many manatees are counted gathering in the artificial warm water sites of power plant discharge canals. Natural warm water sites, such as the entire Crystal River area of Florida, are also meticulously counted because of the number of manatees there seeking refuge from colder waters.