The influence of environmental variables on estuarine dolphins (Sotalia guianensis) spatial distribution and habitat used in the Estuarine Lagunar Complex of Cananéia, southeastern Brazil

The spatial distribution and the use of the habitat by the estuarine dolphin in the Estuarine Lagunar Complex of Cananéia were studied between August 2009 and June 2010. The samplings were taken twice a month in three different segments, through parallel linear transections where environmental variables were recorded: depth, transparency, temperature, seasons of the year, and also the geographical location of the groups that have been seen. A total of 1.031 individuals were seen in 331 different groups, with the greatest occurrence being in the Trapandé Bay, close to the connection with the adjacent ocean. These dolphins were seen in all classes of variables as found. According to the IH, the dolphins used more opaque waters, at depths between ten and twenty meters; salinity of more than 27 parts per million (ppm) and temperatures above 22 °C. By means of generalized linear models, it was confirmed that the spatial distribution of the estuarine dolphins could be explained by salinity (z = 3.661; p < 0.0001) and depth (z = 5.421; p < 0.0001). In the light of the facts here exposed, it is clear that the estuarine dolphins have heterogenous distribution within the estuary as studied and the areas of greater concentration warrant more attention when drawing up preservation strategies.