Distribution and Status of the Guiana Dolphin Sotalia guianensis (Cetacea, Delphinidae) Population in Babitonga Bay, Southern Brazil

The Guiana dolphin Sotalia guianensis is one of the most endangered small cetaceans in the southern Atlantic Ocean. The population abundance and density of this species were estimated in Babitonga Bay in 2000-2003. Sampling was random and stratified, and a line transect method with distance sampling was applied in an area of 160 km super(2). The total length of transects covered was 1251.9 km, with 163 groups of dolphins recorded. Group sizes varied 2-30 (mean, 5.3; SD, 5.6) individuals. Some areas were preferred by the population, and area 3 was considered the core area of S. guianensis in Babitonga Bay. The abundance was estimated to be 245 (95% confidence interval (CI): 142-422) individuals between Dec. 2000 and Nov. 2001, 186 (95% CI: 93-374) individuals between Apr. 2002 and Feb. 2003, and 179 (95% CI: 93-344) individuals between Mar. and Dec. 2003, and the densities were estimated at 1.6 (95% CI: 1-2.7), 1.2 (95% CI: 0.6-2.4), and 1.3 (95% CI: 0.5-3.4) individuals/km super(2), respectively. The highest density was recorded in the central area of the bay.