Occurrence and distribution of marine mammals in a proposed Undersea Warfare Training Range off Jacksonville, FL

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The U.S. Navy has proposed establishing an Undersea Warfare Training Range (USWTR) in an area between 60 and 150 km off the coast of Jacksonville, Florida. To establish baseline information on the occurrence and distribution of marine mammals in this area we conducted aerial and shipboard line-transect surveys and a passive acoustic monitoring program. Here we report the results of aerial and shipboard line-transect surveys conducted between January 2009 and April 2011. During this period, we flew 42,895 km of aerial tracklines and recorded 477 sightings of ten cetacean species (n=5,736 individuals). Tursiops truncatus was encountered most commonly (202 sightings, n=1,699), followed by Stenella frontalis (184 sightings, n=3,213). Other species observed during aerial surveys include Grampus griseus (n=350), Globicephala macrorhynchus (n=174), Steno acutorostrata (n=13), Eubalaena bredanensis (n=118),Balaenoptera glacialis (n=3), Physeter macrocephalus (n=2), Kogia spp. (n=1), and Megaptera novaeangliae (n=1). In 35 vessel surveys totaling 2,486 km we encountered three cetacean species in 77 sightings (n=576). S. frontalis and T. truncatus were observed most often, followed by G. griseus (n=351, 160, and 43, respectively). T. truncatus was observed throughout the entire survey area, but S. frontalis and S. bredanensis were seen exclusively on the continental shelf. All E. glacialis sightings, including a rare observation of an offshore birth, occurred on the western edge of the survey area. All other species were detected only in pelagic waters. Stenella frontalis, T. truncatus, and G. griseus were observed throughout the year (12, 11, and 9 calendar months, respectively); G. macrorhynchus and S. bredanensis were detected from April to October, and all mysticete species were seen only between December and March. This monitoring program, combining a variety of survey modalities, is providing a rich picture of the cetacean fauna in these poorly studied offshore waters.