Biogeographic trends in populations of the shrimp Artemesia longinaris (Decapoda:Penaeidae) on the Atlantic coast of South America

Detecting systematic trends in population parameters along large latitudinal patterns and analyzing them under a macroecological framework can provide useful information for fishery management. This becomes crucial for data-poor fisheries. Combining a metabolic-based argument to explain the decrease in size towards warmer environments (i.e. the temperature size rule, TSR) with the Beverton and Holt life-history invariants (BH) we derived a series of predictions about population parameters and tested them with empirical data from the endemic shrimp Artemesia longinaris (Bate, 1888) along its entire distribution area in the Southwestern Atlantic Ocean (SWAO), from Brazil (21 degrees S) to Argentina (43 degrees S). We also provide novel information on the population structure of A. longinaris captured in Uruguayan waters (34 degrees) filling a relevant gap in a transitional region in the SWAO. We found no relationship between latitude and the maximum carapace length (CLmax), however, both CLmax and the size at first maturity (CL50) showed a negative relationship with maximum temperature consistent with TSR. Changes in CLmax and CL50 presented equal temperature dependence (0.23 +/- 0.165, and 0.25 +/- 0.236, respectively). The BH invariance of the ratio of size at maturity to maximum size of A. longinaris populations captured in the SWAO (average=0.57; sd=0.09) showed no latitudinal trend as expected and was within the expected theoretical value (similar to 0.66). Our results corroborate that at higher latitudes individuals reach sexual maturity at larger sizes than those living in lower latitudes. We also discuss the use of the macroecological approach to provide clues on key demographic attributes that are especially relevant in data-poor fisheries.