Algunos aspectos sobre la estructura populacional del rabil (Thunnus albacares) en el sudeste y sur del Brasil (1969-1977), con presentación de la hipótesis de la migración semestral

Abstract

Monthly length frequency and CPUE of yellowfin tuna caught with longline in Southeastern and Southern Brazil from 1969 to 1977 are presented. The lack of reproductive activity observed during the whole year determined an accurate study of the age group composition, finding groups with permanence approximately between September and February and March and August, which originated the hypothesis that the migration occurs every six months. This hypothesis elucidates some biological aspects, which were difficult to understand, observed in the Atlantic and the Pacific. So, it is suggested that the yellowfin tuna population structure in these oceans is formed by age groups present in the tropical and temperate areas alternatively every each six month period.