The Effects of a New Bridge on Manatee (Trichechus manatus latirostris) Use of the FPL Discharge Canal at Port Everglades, Florida

摘要

The Florida manatee (Trichechus manatus latirostris) is an endangered species that migrates to warm water refuges such as natural springs or power plant effluents during the winter months to escape cold water. The Florida Power and Light (FPL) discharge canal in Port Everglades, Ft. Lauderdale, FL., is utilized as a refuge by overwintering manatees. Construction of a new bridge over the FPL effluent canal had a potential effect on manatee usage of the canal. Discharge is often 10-15° C warmer in the winter season than the surrounding waters of the Intracoastal Waterway. Previous data, including age class and cow/calf abundance from pre-bridge winters (2004-2009), were compared with data from winter 2010, during bridge construction and winter 2011, postbridge construction. No manatees were present at the survey sites during winter until surface water temperatures fell below 22° C. Although monthly mean surface water temperatures were not statistically different between 2008-2009, 2009-2010, and 2010-2011 (21.9±0.4° C, 21.8±1.8° C and 21.4±0.6° C respectively), manatee abundance did vary. 2008-2009 had higher monthly mean numbers of manatees per survey from December through March (29.7, 27.3, 48.1, 2 respectively) than 2009-2010 (0, 30, 10.7, 5 respectively) and 2010-2011 (18.7, 6.7, 0.1, 0 respectively). A Poisson distribution analysis showed a significant difference in adult manatee counts among the study years (α u3c 0.05). No significant differences were found for juveniles and calves. While I cannot decisively state that bridge construction reduced the number of overwintering adult manatees during 2010, there appears to be the potential for an effect.