Abundance of bottlenose dolphins, Tursiops truncatus, in the coastal Gulf of Mexico.

The abundance of bottlenose dolphins (Tursiops truncatus) for many coastal areas of the United States Gulf of Mexico is poorly known. During the spring and fall 1987, we used aircraft and strip transects to estimate bottlenose dolphin abundance within 37 km of the U.S. Gulf shore. Greatest estimated dolphin densities were in the north-central Gulf (spring), northern Florida (fall) and Louisiana study areas (fall) (about 0.30 dolphins/squared km). We estimated the coastal U.S. Gulf population of bottlenose dolphins to be 16,892 +/- 3,628 (95% Cl) and 16,089 +/- 3,338 in spring and fall, respectively. Bottlenose dolphins were found throughout the U.S. Gulf waters searched, but herds offshore of Texas were concentrated near passes and Louisiana herds were more common in and near eastern bays. Our estimates are one of the first assessments of the abundance and density of bottlenose dolphins throughout the coastal U.S. Gulf and may provide useful baseline estimates.