Weeki Wachee River System Recommended Minimum Flows and ...

Figure 5-2
Abundance Response to Flow – pinfish
5.3 Manatee
5.3.1 Descriptive (Adapted from Laist and Reynolds (2005))
The Florida manatee (Trichechus manatus latirostris) is a marine mammal subspecies
of the West Indian manatee and is found only in the southeastern United States. The
U.S. Fish and Wildlife Service (USFWS 2001) estimates a Florida population of around
3,276 animals based on a Florida-wide count during January 5-6, 2001. A
subpopulation of approximately 400 animals is associated with the springs north of
Tampa Bay.
Many animals succumb annually to collisions with boats and from the effects of a suite
of neurotoxins (brevetoxins) produced by the red-tide dinoflagellate Karenia brevis. The
Florida manatee is Federally classified as an 'endangered' species, but on April 9, 2007
the U.S. Fish and Wildlife Service recommended 17 that the designation be reduced from
endangered to 'threatened'.
Manatees are poor thermal regulators. Animals exhibit a high degree of thermal
conductance (poor insulation) with relatively low metabolic rates (Rouhani et al. 2006)
and are generally vulnerable to exposure to temperatures below 20 o C, although some
17 http://www.fws.gov/southeast/news/2007/r07-057.html
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Proposed Minimum Flows and Levels for Weeki Wachee River Page 82 of 164
Biological Characteristics