Utilização de hábitat pelo boto-cinza, Sotalia guianensis (Cetacea, Delphinidae), na região do Complexo Estuarino Lagunar de Cananéia, São Paulo

Abstract

In several studies regarding habitat use it was concluded that environmental characteristics effectively influence distribution and abundance of food resources, which determine species entire distribution in a given area. The areas that animals spend most of their time are called key habitats. The estuarine dolphin habitat use in the Estuarine Complex of Cananéia – Iguape- Paranagua region was studied from August 2009 to June 2010. Samples were monthly collected in three sectors, using parallel linear transects. In two out of four field trip were registered geographical location, composition and size of spotted groups. In the beginning, middle and end of each transection the following environmental descriptors were collected: water depth, temperature, transparency and salinity. In the other two field trips the transections were traversed to record behavioral activities - feeding or moving - of fouded groups. In total, 330 groups with 1028 individuals were spotted. The sector with major occurrence of groups was the Trapandé Bay, close to the conection with adjacent ocean. In this place, feeding was the most observed behavior, and the frequency of individuals was constant in every season, differently of the other sectors. Group size varied from 1 to 14 individual, but most frequent records had two or three individuals per group. Infants were recorded in all field trips, especially in the rainy season. There was a higher frequency of estuarine dolphins in mornings than afternoons, as also higher frequency in spring tides flood when compared to other tides. The estuarine dolphin occurred in every values classes of environmental descriptors analyzed. The highest occurrences were recorded in turbid waters; depths between 5 and 15 m, salinity above 20 ppm and temperatures above 20ºC. For these reasons, it is clear that the estuarine dolphin showed a heterogeneous distribution in the studied estuary and the areas of greatest concentration deserve more attention in developing conservation strategies.