Paulo, BraziL Emailfransozo@ibb.IlI.U) Yp.br ABSTRACTThe influence of environmental factors on the abundance and spatial-tempotal distribution of the sltrimp Xiphopenaeus kroyeri was investigated. in southeastern Brazil over 2 years. Monthly collections were conducted in Mar Vrrado, Dbatuba and Dbatumi!im Bays using a commercial shrimp fishing boat equipped with 2 "doubJe.-rig" nets. Each bay was divided into 6 samplJng stations, all of which were less than 25 m deep. The spatial distribution of X kroyeri differed among Bays. Highest abundance values were recorded in areas where silt and clay comprised more than 70% of the bottom sediment Abundance of X kroyeri followed a seasonal trend, heing higher during fall and winter, when intrusions of tropical waters are frequent, causing an increase in salinity (> 35%") and temperature (> 21° C). A clear decrease in shrimp abundance followed a decrease in bottom temperature « 20" C) during spring and summer due to the influence of cold water currents, particularly the South Atlantic Central Water. These results suggest that sediment type, salinity, and temperature are among the most important variables affeclJng the spatial and seasonal distribution of this species.

The in£uence of several environmental factors on the abundance and spatial^temporal distribution of the shrimp Artemesia longinaris were investigated from January 1998 to December 1999 in the Ubatuba region of Sa‹ o Paulo State, Brazil. Collections were performed monthly in the bays of Ubatumirim (UBM), Ubatuba (UBA) and Mar Virado (MV). Six sampling transects were established in each bay, four were parallel to the shore line, and two were next to the rocky shores. A commercial shrimp ¢shing boat equipped with two 'double-rig' nets was used. A total of 11,503 individuals was collected, including 1633 from UBM, 6344 from UBA and 3526 from MV. The majority of the captured specimens came from the deeper areas (15 to 20 m) with high salinity (34 to 36 ppt). The highest abundance of A. longinaris in Ubatuba bay was recorded in areas where ¢ne and very ¢ne sand comprised more than 70% of the sediment. Moreover, the abundance of A. longinaris followed a seasonal trend, being higher during the summer, when intrusions of cold South Atlantic Coastal Waters (SACW) are frequent. Thus, type of sediment, temperature and salinity are determinant factors in the distribution of A. longinaris in the studied region.

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The impact of shrimp fisheries in tropical regions has become comparable to the world's most intensively exploited temperate shelf ecosystems. The increase in the fishing fleet in south-eastern Brazil and the decrease in landings of profitable shrimp species have contributed to the incorporation of additional species into those fisheries. The goal of the present study is to investigate the influence of environmental factors on the abundance patterns of shrimp communities on the south-eastern coast of Brazil, over a period of two years. Monthly collections were conducted in the Ubatuba and Caraguatatuba regions using a commercial shrimp fishing boat equipped with 'double-rig' nets. Each region was divided into 7 sampling stations up to 35 m deep. The relationship between the environmental factors and the abundance patterns in the shrimp communities was assessed using a canonical correlation analysis (CCorrA). The first set of variables used during the CCorrA included environmental characteristics and the second set of variables the abundance of the studied species. A total of 374,915 individuals were collected during the present study. Xiphopenaeus kroyeri showed the highest abundance (273,127), followed by Artemesia longinaris (73,422), and Pleoticus muelleri (15,262). In the first root, depth and temperature showed the highest factor loadings (0.9 and 20.7) and canonical weights (0.6 and 20.4). These environmental factors were strongly associated with the abundance of X. kroyeri (factor loading ¼ 2 0.9 and canonical weight ¼ 2 0.9). The second root demonstrated a positive relationship between abundance of P. muelleri and depth, and an inverse association with bottom temperature. The abundance patterns of X. kroyeri and P. muelleri were strongly affected by the water mass South Atlantic Central Water (cold waters ¼158C), which can lead to a temperature decrease in deeper areas (.15 m). Thus, the opposite abundance trend for depth of these species might reflect bathymetric variation in temperature, a clear example of distinct behavioural differences of species of different origins, either tropical (X. kroyeri) or subantarctic (P. muelleri). The low overall association between environmental parameters and shrimp abundance patterns indicates that each studied species might have responded idiosyncratically to environmental variation, such that a general community-level response was not apparent. However, other confounding factors such as intraspecific migration patterns might have also played a role in generating the observed patterns.

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