Population and reproductive biology of the seabob shrimp in Santos Bay, São Paulo

Abstract

We investigated the sexual maturity, reproductive period and juvenile recruitment (both associated with salinity and temperature of bottom water) and sex-ratio of Xiphopenaeus kroyeri in Santos Bay, São Paulo. Monthly samples were obtained from June 2008 through May 2009 along four transects. Individuals were measured and sexed, and the developmental stage of the reproductive system was macroscopically determined. The mean carapace length of females was larger than that of males. Females attained physiological maturity with 25.5 mm and males, with 16.8 mm. The reproductive period was continuous, with higher proportions of reproductive females in autumn. Although not significant, in February occurred a peak of reproductive females similar to that registered in March. An intermediate peak of these females occurred between August and October and it contributed to the recruitment in summer. The smallest amount of juveniles after the main peak of spawning (February, March and April) can be explained by migration or consequences of open access for fishery that occurs on June. The overall sex-ratio was approximately 1:1. However, when considering the spatial distribution, we observed a greater amount of reproductive females in shallow waters in the bay. The differential distribution between the sexes could be associated with appropriated areas to spawn. The current legal off-season occurs between March and May, and, according to our results of the frequency of reproductive females, we suggest the inclusion of February in the off-season.