Abundance and distribution of juvenile pink shrimps Farfantepenaeus spp. in a mangrove estuary and adjacent bay on the northern shore of São Paulo State, southeastern Brazil

The juvenile recruitment periods of two important fishery resources of the Brazilian coast, the pink shrimps Farfantepenaeus brasiliensis and F. paulensis, were investigated in the Ubatuba region, state of São Paulo, Brazil. Sampling was carried out monthly between July of 2005 and June of 2007 on four transects in the Indaia estuary, and on four additional transects in the adjacent Ubatuba Bay. A total of 1,225 specimens of F paulensis were analyzed, 906 from the estuary and 319 from the bay. The vast majority of F brasiliensis specimens (954) were captured in the bay, except for two individuals that were collected in the estuary. Juveniles of F. paulensis were found in almost all months in both years in the estuary, with two pronounced peaks in each year, one between February and March (summer) and another between May and July (autumn and beginning of winter). Increased abundance of juveniles was observed in the bay in two periods, which occurred 1 or 2 months after the two main peaks observed in the estuary. The recruitment of F. brasiliensis showed strong seasonal patterns in both years (March to May). For both species, a significant positive correlation (Spearman, p <0.05) was found only in the bay, between the abundance of juveniles and the bottom-water temperature during the study period. Salinity was the preponderant factor affecting the differential distributions of juveniles of both species. Both species preferred higher salinities, and only F. paulensis tolerated wide variation in this factor. Salinities lower than 15 parts per thousand are assumed to limit the establishment of F brasiliensis in the estuary. The occurrence of juvenile development in the bay and not in the estuary (particularly in F brasiliensis), as usually suggested in the literature, can jeopardize the entire fishery stocks of these species in the region, because the bay contains the main fishing grounds for the seabob shrimp Xiphopenaeus kroyeri, one of the species most sought after by the fishing fleets. The study indicated that the small estuary and larger bay, which differ greatly in salinity, provide a differential habitat choice for these shrimp species.