Aerial Surveys of Endangered and Protected Species in the EMPRESS II ship TrialOperating Area in the Gulf of Mexico

摘要

Aerial surveys were conducted from November 1991 to June 1992 in an 81.5 x 110 kmarea approximately 50 km south of Mobile, AL. Line transect methods were used to estimate abundance of sea turtles and cetaceans over a 6-month period (November to April). Sonograms and spectrograms of cetacean vocalizations proved useful for species identification. Passive acoustical methods were employed to determine the presence of cetaceans beneath the surface. Three species of sea turtles (Dermochelys coriacea, Caretta caretta, Chelonia mydas) and at least four species of toothed whales (Gobicephela macrorhynchus, Delphinus delphis, Tursiops truncatus, Stenella spp.) were observed and/or recorded in the area. In addition, sperm whales (Physeter catodon were recorded south of the area. A total of 83 sea turtle sightings and 116 cetacean sightings were made in the area during the 6-month study. Most sea turtles were observed as singles, whereas dolphins were generally found in groups of 2 to over 100. Sea turtle density was estimated to be 0.01 turtles/kM2; cetacean density was estimated at 0.78 odontocetes/km2. Densities of both sea turtles and cetaceans were less than what has been reported for other areas of the northern Gulf of Mexico. An adjustment factor, based upon acoustic data, of 1.3 is suggested as a correction factor for submerged cetaceans.... Acoustics, Marine mammals, Marine turtles, Biota, EMPRESS.