Changes after 20 years in the population structure of the South American endemic shrimp Artemesia longinaris (Crustacea, Decapoda) on the southeastern Brazilian coast

Abstract

The present study compared the population structure of the shrimp A. longinaris during two distinct periods (November/1988 to October/1989 and November/2008 to October/2009) in the Fortaleza Bay. We used Pearson correlation analysis to verify a possible association between temperature and cephalothorax length (CL) of the obtained individuals. 2412 females and 676 males of A. longinaris were captured in the first period; 843 females and 409 males, in the second. The mean size of shrimp was 15.6 mm CL in the first period and 14.3 mm CL, in the second (U=1066671.0; p < 0.05). Larger individuals were sampled at lower temperatures (Pearson's correlation; r2= -0.80; p < 0.05). In both periods of sampling, we have got adult females larger (mean sizes) than adult males. In addition, for both periods the sex ratio was in favor of females (p < 0.05). The intense trawling activity as well as the water temperature may have caused a sampling of smaller individuals in the second period. The sex ratio favoring females is possibly a result of migration of females to shallower regions, just after mating. After 20 years, only the mean size of the shrimp has changed among the analyzed aspects for A. longinaris.