Hábito alimentar do boto-cinza, Sotalia guianensis (Cetacea: Delphinidae) na Baía de Guanabara, Rio de Janeiro

• Autor(a) principal: Melo, Cláudia Lucas Corrêa de
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/13902
• topic: Diet; Delphinidae; Teleosts; Cephalopods; Dieta; Delphinidae; Teleósteos; Cefalópodes; CNPQ::CIENCIAS EXATAS E DA TERRA::OCEANOGRAFIA::OCEANOGRAFIA BIOLOGICA

In this work, aspects of feeding habits of the Guiana dolphin, Sotalia guianensis (Van Beneden, 1864), were studied in Guanabara Bay (N = 26), with the aim of characterizing its diet and comparing the results with those from other species of the Delphinidae family (N = 31). The stomach contents analyzed were collected from specimens stranded on the beaches of Rio de Janeiro between 1990 and 2009. The methodology is based on washing stomach contents through 1 mm mesh sieves, as well as on the identification of the food items remained, such as teleost otoliths and cephalopod beaks. The length of the food items was used to estimate the length and weight of preys using regression equations found in the literature for these species. Teleosts constituted the most abundant prey in the stomachs of Guiana dolphin (N = 325), being followed by cephalopods (N = 76) and finally by crustaceans (N = 16). Were identified 17 species of teleosts belonging to 10 families, as well as two species of cephalopods from the Loliginidae family and one species of crustacean from the Penaeidae family. The most important species in Guiana dolphin diet, according to the index of relative importance were the whitemouth croaker (Micropogonias furnieri), the weakfish (Cynoscion jamaicensis) and atlantic midshipman (Porichthys porosissimus). Among cephalopods, the squid Loligo plei was the most representative prey in the diet. Regarding the size of prey, most consumed teleosts had the length varying between 11 and 20 cm (15.4 ± 5.5 cm), characterizing the consumption of juvenile fishes. The cephalopods mantle length ranged from 6 to 15 cm (11.8 ± 4.2 cm). A great similarity was observed in the diet composition of females, males, and juveniles of Guiana dolphin, however, the mean length and biomass of fish differed between those consumed by adults and those preyed by juveniles (Kruskal-Wallis, p<0,05, posteriori comparison of medians). Species richness was higher in warm seasons, as well as the diversity and evenness index, which may be related to a greater availability of prey during these seasons. Proportions of the preys consumed varied, however, the composition of the diet, as well as the habits and size of prey, remained similar between seasons. While all species consumed by Guiana dolphin presented coastal habits, the other delphinids species consumed preys of larger distributions, which could be related to a greater movement of these species along the coast. This study showed that there are variations in food habits of Guiana dolphin in Guanabara Bay and indicates that this species feeds on the available resources in the region.