Overlap of the reproductive cycle and recruitment of the four main species caught by the purse seine fleet in Brazil
The purse seine fleet in southeastern and southern Brazil has the Brazilian sardine Sardinella brasiliensis as the target species, and fishery management is based solely on its life cycle. This study aimed to analyze a possible overlap of the reproductive cycle and recruitment of the main species caught by seine fleet. During the daily program of industrial fishing monitoring in the ports of Itajaí and Navegantes (Santa Catarina) biometrics were performed twice a month at landings between 2000 and 2013 for posterior analysis in laboratory abroad. The samples analyzed did not include part of the reproductive period and the recruitment due to the closed seasons. The size at first maturity (L50) was obtained by adjusting the proportion of adult females to a logistic model. The reproductive period was determined by analyzing gonadosomatic index and proportion of the maturation stages. Recruitment was determined from the length distribution and the ratio of immature throughout the year. L50 determined was 18.60 cm for S. brasiliensis, 19.58 cm for Opisthonema oglinum, 18.48 cm for Chloroscombrus chryssurus and 21.22 cm for Scomber japonicus. The analyzed species overlapped spawning period between November and April and recruitment in June and July. In the case of directing fishing effort to these non-target species, the possibility of inclusion of these species in closed seasons of target species could ensure a better management and consequently the sustainability of this activity.