Diel comparison of the catch and size of the shrimp artemesia longinaris (dendrobranchiata, penaeidae) in the ubatuba region, northern coast of the state of São Paulo

Artemesia longinaris Spence Bate, 1888 is an endemic shrimp of the western South Atlantic. The objective of the present study was to analyse diel variation in the abundance and size of A. longinaris in the Ubatuba region, state of São Paulo, Brazil, during the year 2000. During each season of the year, collections were made during the day and night along 8 transects at depths ranging from 5 to 40 m. The water temperature and salinity was measured during sampling, and sediment samples were taken for the analysis of texture. The shrimp were more abundant at night at all stations and transects, except at a depth of 15 m during the spring (chi(2), p < 0.05). In the study region A. longinaris conformed to the burying model, in which shrimp are active during the night and only occasionally emerge during the day. However, in periods when juveniles are highly abundant and a decrease in temperature occurs, the shrimp established themselves in shallower areas of the bay (5 to 15 m) where the main sediment was silt and clay, and not in deeper areas (20 to 40 m). In this case, we observed a change in the burying pattern: individuals were active during the day as well as at night. Only in spring it was possible to observe the decrease in average size of individuals collected during the day, due to the peak of juveniles in this season. As a consequence, the sediment type and life cycle of the species appeared to modify the yield of shrimp during the periods analysed.