Aspectos da estrutura populacional da Anchoa januaria (Actinopterygii, Engraulidae) na Baía de Sepetiba e diferenciação morfológica entre duas localidades da costa sudeste-sul do Brasil

Abstract

Sex ratio of Anchoa januaria (Steindachner 1879) was described in the Sepetiba bay. The aim was to test the hypothesis that sexual dimorphism occur due to different reproductive roles, and that there is spatial and temporal changes along the individual development. Additionally we search for morpho-meristics variation in the species between two areas along the Southeastern-South Brazilian coast due to eventual isolation that could be favored by the group behavior. We colleted fishes from the Sepetiba bay, between september 1998 and august 1999, and examined fishes from Paraná coast deposited in the Museu the Zoology from University of São Paulo. A stratified structure of A. januaria population was detected, with the lower river reaches showing adults (CT=60-80 mm) only, while juveniles and adults (CT=32-80 mm) occurred in the beach which are used as rearing grounds. Females reach larger size than males, and it is associated to larger intestine length, which enable accumulate a larger amount of energy to the reproductive process. Sex ratio of the “spawning schools” is well balanced (1 female : 1.02 male) in the river sites, and females biased in the beaches (1.63 female : 1 male ). Comparative morphometric studies between specimens from Rio de Janeiro (C.S.F e b.S), and Paraná (r. I e b.P) indicate heterogeneity in corporal structure, with higher integration for Paraná individuals, which population is more homogenous, suggesting that individuals are using a more stable environment for its development. Two distinct groups were detected suggesting a possible populations segregation. Such differences could be linked to absence of genetic interchanges between the species from the two locals, favored by reproductive behavior and low tolerance to salinity of this species.