Abstract This study investigated the temporal abundance, periods of reproduction and recruitment, gonad sexual maturity, and population structure of the swimming crab Achelous spinimanus (Latreille, 1819) in Macaé, a region of the Brazilian coast affected by upwelling events. The samples were collected monthly during one year. The crabs were counted, sexed and measured for maximum carapace width (MCW). Four developmental stages were described in males and females. Environmental variables as temperature, salinity, organic matter and Phi were measured. A Principal Components Analysis indicated that environmental variables were strongly correlated with seasons, affecting the abundance of this species, which was high during summer and autumn. The periods of reproduction and recruitment were also seasonal, with a peak of females with developed gonads and ovigerous females during autumn and immatures during summer and autumn. Males and females did not differ in size at gonad sexual maturity, estimated at 39.9 and 42.9 mm MCW, respectively. The environmental conditions in this upwelling region may have induced this population of A. spinimanus to show different characteristics and behaviors from other populations on the Brazilian coast, since alterations linked to the periods of reproduction and recruitment, as well as the population structure and distribution, may reveal different survival strategies of the species.

Abstract The spatio-temporal distribution of juveniles of the pink shrimps Farfantepenaeus brasiliensis (Latreille, 1817) and Farfantepenaeus paulensis (Pérez-Farfante, 1967) in the Ubatuba region (SP) was investigated. Sampling was performed in the bays of Ubatumirim (UBM), Ubatuba (UBA) and Mar Virado (MV). A total of 2,018 F. brasiliensis and F. paulensis were collected. The largest catch of juveniles of both species occurred in UBA (N = 867), followed by UBM (N = 729) and MV (N= 422). The bottom sediment in MV had the highest silt and clay content, which explains the negative correlation of the substrate with the abundance of both species. Temperature was positively correlated with the abundance of both species. Juveniles were highly abundant in shallower areas in the summer of 1998. The high rainfall in this El Niño period may have lowered the salinity in estuarine waters and led the shrimps to move to coastal areas in search of higher salinities such as in bays. With this unusually early reduction in salinity, individuals migrated to the bay before the closed season began and thus became more exposed to fishing. We confirmed that monitoring environmental variations, especially in El Niño years, is essential for understanding the distribution patterns of juveniles of both species.

This study evaluated the spatial-temporal distribution of the abundance of Caridean and Penaeid shrimps during the period of two years in the coastal region of Macaé, state of Rio de Janeiro, southeastern Brazil, using ecological indices (Shannon-Wiener diversity and Pielou's equitability). Monthly samples were carried out from March 2008 to February 2010 distributed in six stations located Inner Area (5, 10 and 15 m depth) and Outer Area (25, 35 and 45 m depth) using a commercial fishery boat equipped with an otter-trawl net. Water samples were taken for determination of temperature and salinity, and sediment samples for determination of texture and organic matter content. Ten species of Decapoda, including Penaeids and Carideans, have been identified, from a total of 49.941 collected individuals. There was a strong correlation between Penaeid and Caridean shrimps abundance and the bottom temperature and sediment. It could be inferred that Artemesia longinaris acted as a keystone species regulating the shrimps community in the coast of Macaé, given that both species diversity and equitability were controlled by the migratory events of A. longinaris following the variations in temperature caused by the SACW. These results provide as a basis for management actions to prevent significant losses of population stocks since it is an important marine area considering of its peculiar relevance to the fishery.