In three USGS-led studies — the first comprehensive population analysis published in 9 years — scientists documented survival, reproduction, and population growth rates of the endangered Florida manatee. The Florida Fish and Wildlife Conservation Commission, Mote Marine Laboratory, and the Florida Park Service collaborated in the research, published in the July issue of the journal Marine Mammal Science.

Population-Growth Rates

"Over the past 10 years, the annual population growth rate in two of the regions is healthy, one region appears to be declining, and one region is probably holding steady. That's what the science says," Michael Runge, lead scientist for the USGS said. "We estimate that manatee populations in the Northwest and Upper St. Johns River regions have been growing annually at 3.7 percent and 6.2 percent, respectively. These estimates are in line with previous studies and, leaving a margin for error, suggest healthy growth of those populations."

The report concludes that the estimated annual growth rate for the population in Florida's Atlantic region is 1.1 percent, but the margin of error in this estimate is large enough that it is possible the population is stable or slightly declining. In the Southwest region, the estimated population growth rate is negative (1.1 percent per year); however, the margin of error in this estimate is larger than in the other regions.

"The estimates for the Atlantic and Southwest are of concern, because these regions make up most of the manatee population," said Runge.

These findings estimate annual population growth rates over the past decade, using survival and reproductive rates from the two companion st
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Contact: Michael Runge
michael_runge@usgs.gov
301-497-5748
United States Geological Survey
4-Aug-2004