Estimativa de parâmetros populacionais, área de vida, mortalidade e interações da atividade pesqueira sobre a população de botos-cinza (Sotalia guianensis) (Van Bénéden, 1864) (Cetacea, Delphinidae) na Baía de Sepetiba (RJ)

Abstract

The thesis contains three chapters with the main goal to fulfil knowledge gaps that are extremely important to support conservation of Guiana s dolphin population in Sepetiba Bay and also for the whole species. The thesis presents a general introduction about the species and study area, and also describes the methodologies using thef photo-identification tools to study the home range size and population parameters, and the antrophogenic pressures on small cetaceans along the brazilian coast. In the first chapter was observed that the diurnal movement of group of dolphins did not present any different seazonal patterns related to distances traveled and movement rate. The spacial use of guiana dolphin populaction size was 47% of the total sampled area, and the groups were found spread between the entrance and interior, while the aggregations were concentrated next to the central island. The individuals are not randomly spread in Sepetiba Bay, with some dolphins using more frequently the entrance of the bay, while other individuals use the interior and others that do not present preferences neither for the entrance nor for the interior. In the second chapter was observed a total of 826 individuals cataloged and the number of dolphins photo-identified for the first time in each occasion ranged from 91 (2011) to 306 (2012). The aparent survival and the recapture rate, from 2006-2009, were respectively 0,88± (0,04), 0,49± (0,04). The population size estimation between 2005-2009 and 2012 using the full likelihood closed population model were (2005; N=501; IC= 333-756), (2006; N=794; IC= 521-1210), (2007; N=709; IC= 625-850), (2008; N=978; IC= 863-1163), (2009; N=939; IC= 790-1117), (2012; N=768; IC= 588-1004). In the third chapter was possible to observe that from a total of 201 carcasses of dolphins, 24,8% (n=50) presented fishery interaction evidence. The proportion of dead males (1,35:1) was significantly higher, and both sexes presented a higher mortality on adults age class. An increasing mortality of dolphins along the years was detected, mainly from 2010, where (63,68%) of the total carcasses were recovered. There was also a sasonality in the mortality with a higher frequency during winter and seconde semmester, corroborating with data of higher fishing effort, target species and gillnets that are recognized to bycatch dolphins. The mortality of dolphins in Sepetiba Bay is increasing along the last years and overcome tree times the estimated Potential Biological Removal.The present study had the goal to fulfil knowledge gaps in areas of ecology and conservation, as well as, to help to identify the threats to mantain this population in order to support public policies for the conservation of the species