Minke whale Balaenoptera bonaerensis (Burmeister) (Cetacea, Balaenopteridae) population structure in the breeding grounds off South Atlantic Ocean.

摘要

A group composition study of the minke whale, Balaenoptera bonaerensis (Burmeister, 1867) captured in the waters of Costinha, Paraiba, Brazil, was conducted with the aim of better understand the reproductive behavior of this species as well as the ecological characteristics of that population. In this study, the information gathered by Superintendencia para o Desenvolvimento da Pesca and Companhia de Pesca Norte do Brasil from 1975 to 1985 about the whale's group size and composition, sexual proportion, sexual maturity of the captured whales was analyzed. The groups found in the waters of Costinha were in general of small size and composed by animals of both sexes, with a greater proportion of sexual mature and female animals. Calves, lactating or pregnant females were rarely found. That population concentrated in higher number in the waters of Costinha between September to October, the most important period for the species conception. A great number of conceptions might occur at this time in the area. The absence of lactating females and calves in the population demonstrate that births do not occur in this area. Strandings and sightings of young minke whales in the South America east coast (between 25 degrees S e 40 degrees S) suggests that births occur at medium latitudes of this region, where the water temperature is inferior to that one in the Northeast Brazilian Coast. In that way, the possibility of the existence of distinct areas to births and breeding activities of minke whales in the South Atlantic Ocean might be considered. The polygamy is a reproductive behavior of minke whale, observed by the composition and sexual proportion of groups composed by sexual mature animals in this breeding ground.