Habitat use of the Guiana dolphin, Sotalia guianensis (Cetacea, Delphinidae), in the Caravelas River Estuary, eastern Brazil

Habitat use patterns of the Guiana dolphin (Sotalia guianensis) were assessed in the Caravelas River Estuary, eastern Brazilian coast (17°54’S, 39°21’W). During 191 surveys (2002-2004), 187 groups were sighted. The Arcview 3.1 software was used to create a GIS environment that included the distribution of dolphin sightings, a 5x5km quadrats grid, and the bathymetry of the study area. Each quadrat was characterized according to environmental variables such as depth, contour index, distance from sand banks and distance from the coastline. The Caravelas River mouth was found as the core area of the dolphins. Guiana dolphins did not use the several classes of environmental variables homogeneously, occurring more frequently in shallow waters, closer to sand banks and closer to the coastline. Also more dolphins occurred in areas with flatter bottoms and in waters with salinity ranging from 35 to 38ppm, despite dolphins being sighted in waters 14km inside the river. Dolphins used a wide range of habitat types but the Caravelas River mouth seems to propitiate the most adequate conditions for foraging strategies or concentration of prey.

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