OrganizaÃÃo social de elasmobrÃnquios na Reserva BiolÃgica do Atol das Rocas, Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Many animals tend to form social groups, segregating individuals from different classes, such as males and females, adults and subadults, and even large and small specimens of the same species. In order to better understand the behavior of elasmobranches in an insular environment, the social organization of the nurse shark, Ginglymostoma cirratum, (Bonnaterre, 1788), the lemon shark, Negaprion brevirostris (Poey, 1868), and the southern stingray, Dasyatis americana (Hildebrand &Schroeder, 1928), was studied during seven scientific expeditions to the Biological Reserve of the Atol das Rocas throughout summer (March, April and May) and winter (August, September and October) seasons. The survey was carried out in eight different sites: Barretinha, CemitÃrio, Podes-Crer, SalÃo, Tartarugas, Ãncoras, Laguna e Farol. The underwater visual censuses were conducted with snorkeling, on both high and low tide, using intensive search. Three elasmobranch species were identified, with a total of 780 individuals. The results showed a significant difference on the total abundance of G. cirratum e N. brevirostris between summer and winter, with the largest number of elasmobranches occurring during winter. There was also a spatial segregation of the three species of elasmobranches, with a preference of specific habitats by each species. A segregation between small and large animals was found for some of the studied sites. A sexual segregation was also found, with adult males of all species showing a more restricted distribution and a lower abundance than adult females, particularly for G. cirratum, which showed significant differences of abundance between seasons. The social organization of the elasmobranches in Atol das Rocas seems to be related with habitat preferences of each species; with the refuge behavior of small individuals, especially newborns and juveniles, in nursery sites protected from the adult aggression/ predation; and the reproductive season of G. cirratum. Additionally, observations on the behavior, both inter- and intraspecific, of all studied species were made with the occurrence of following behavior, habitat partition and agonistic interactions.

ASSUNTO(S)

spatial segregation oceanografia sexual segregation elasmobrÃnquios elasmobranch segregaÃÃo espacial social organization segregaÃÃo sexual organizaÃÃo social oceanografia

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