Caracterização espaço-temporal da população de boto-cinza, Van Bénéden, 1864 (Cetacea: Delphinidae) na Baía de Benevente, Espírito Santo, e implicações para a conservação

Abstract

In Brazil, research with cetaceans has been intensified the Guiana dolphin, Sotalia guianensis, has gained distinction because of the increasing number of studies regarding its conservation status. An estuarine dolphin population in the southern state of Espirito Santo was chosen for this study due to lack of previous studies. Between 2012 and 2014 efforts were done by methods covering a spatio-temporal scale. A total of 117 boat trips were made (472.4 hours), from December 2011 to November 2014. The application of photo-identification technique allowed the identification of 60 individuals. Most photo-identified individuals were faithful to this area during this period and in various degrees of residence. Among individuals photo-identified no difference between the sizes of home ranges and from the overlapping areas of life of individuals and sighted groups, it observed that the portion farther north of the sampled area of Benevente Bay was most commonly used by dolphins. The largest home range previously reported for the species were recorded in this study. From the mark-recapture method was estimated 59-80 individuals. Estuarine dolphin groups were sighted in all the years and seasons, corresponding to 54.38% of the effort days. On average, the groups were composed of eight individuals, and mostly we observed the presence of calves, as well as over all the years and seasons. Since the presence of calves were correlated to the increase in size of the groups. The observations of the behavior of the sighted group found that the most common behavioral state was foraging, followed by the displacement, socialization and resting. The occurrence and fidelity of this population of Guiana dolphin in Benevente Bay, as well as the presence of calves in all seasons and prevalent behavior was foraging, all are indicators of the importance of Benevente Bay as an feeding and breeding area. In this context, the size of this population associated with anthropogenic threats already identified puts this population in a state of attention to possible management actions.