Environmental Factors and Their Effect on the Seasonal Aggregations of the Florida Manatee (Trichechus manatus latirostris) in the Port Everglades and Intracoastal Regions of Fort Lauderdale, Florida, 1999- 2009

The Florida manatee (Trichechus manatus latirostris) is one of the most endangered marine mammals in United States. The seasonal distribution of the Florida manatee is influenced by feeding locations in, the summer and proximity to warm-water refuges during colder months. During the winter manatees adopt a refuging strategy and aggregate in warm-water refugia when the ambient water temperature falls below 20°C (68°F). We monitored manatee abundance at the Florida Power and Light Plant in Port Everglades (PPE), Florida, its effluent canal, and the surrounding Intracoastal Waterway from 1999 - 2009. Raw manatee count data and catch per unit effort (CPUE) were compared to numerous environmental factors including air and water temperature; heating degree-days; and diurnal and tidal cycles. These data were also compared to annual synoptic aerial surveys and statewide mortality data. Total manatee counts and CPUE were correlated (R2 = 0.8733) as were CPUE and heating degree days (R2 = 0.6995) for the period 1999 - 2004. Manatee abundance at PPE paralleled the results of the statewide synoptic surveys and other aerial surveys (1999 ~ 2004). More manatees were seen in PPE in the morning compared to later in the day (P \u3c 0.05) during the years 2004 - 2007. The probability of observing a cow/calf pair was greater during high tide compared to low and mid-tides (P \u3c 0.05) for the period 2004 - 2009. Total manatee occurrence and the presence of cow/calf pairs were both significantly correlated with water temperature (P \u3c 0.05) for the period 2004 - 2009. These results can impact the scheduling of future synoptic surveys (e.g. likely to achieve maximum counts if conducted in the morning at high tide on cold days). This study also documents the importance of Port Everglades as a wintering refuge for the Florida manatee