What 2009 Florida Manatee Survey Results Mean
Despite Record Numbers Seen Species Population Trend is Not Clear
Jan 29, 2009
It would seem that the results of the 2009 Florida manatee (Trichechus manatus latirostris) survey would be cause for celebration but the one day count is not an accurate estimate of total population. Nor does it show whether manatee numbers are increasing in Florida or not.
Coupled with the increased death rate in 2008 the information researchers are getting a better picture of manatee activity in Florida but improved survey methods will be needed to provide the population estimate needed for appropriate manatee management.
Record Numbers of Manatees Seen in Florida Survey
In January of 2009, 3,807 Florida manatees were counted throughout the state. The previous high in 2001 was less than 3,300. But the Florida Fish and Wildlife Conservation Commission is quick to point out that the surveys are a snapshot of manatee numbers not population estimates.
The weather aided in creating the high counts. Cold fronts passing through the area concentrated the manatees in warm water sites. And the skies were clear on the day of the count, allowing for aerial surveying.
High Number of Manatee Deaths in 2008
Florida recorded 337 manatee deaths 2008, a number second only to the record set in 2006 of 417. Perinatal losses, dependent calves that die near the time of birth and not of direct human causes, accounted for 101 of the deaths. Most of these occurred in Brevard County where there is an important manatee calving area.
Boat accidents resulted in 90 manatee deaths. Collisions with watercraft are a significant problem for this slow moving species. Mortality rates from boat accidents are highest in Southwest Florida where manatees congregate in the warm waters of the Orange River near the Florida Light and Power plant during cold weather.
Interpreting the Manatee Survey Results
Having optimum weather for surveying may have contributed to the high number of manatees counted. The manatees were congregated in a few areas and were easy to see. But the fact that the counts were 500 animals higher than the 2001 count when similar weather conditions occurred may be good news.
The high mortality rate in 2008 must also be viewed with some caution. As people become aware of the threats facing the manatee, they are more likely to report finding a carcass. In addition, in areas where the manatee population is growing, there will be increases in natural mortality as that population ages.
Improved Manatee Survey Methods Needed
It is known that manatee populations are increasing in Northwest Florida and in the Upper St John’s River and that in Southwest Florida they are in decline. The situation on the east coast is not clear. Researchers are working on improved survey methods and attempting to create a model which can predict population trends. This information is needed determine the real status of manatees in Florida, including protecting critical habitat to ensure the species does not face extinction.
Read about the rescue of a manatee on Cape Cod here.
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