Assessing the Population Structure of the Southern Brown Shrimp Farfantepenaeus subtilis (Perez-Farfante 1967) Using Different Sampling Methods

We analyzed the population structure of Farfantepenaeus subtilis off Sergipe, northeastern Brazil, comparing different sampling methods. Samples were obtained between March 2015 and May 2016 from the commercial shrimp fleet based in the fishing ports of Aracaju (only shrimps categorized by size: small, medium, and large) and Pirambu (shrimps + bycatch), both operating in the same area. Each specimen was measured and weighed: total length - TL (mm), carapace length - CL (mm), and live weight - LW (g). The sex and maturity stage were identified. A total of 4,657 specimens was sampled, with 91.5% originating from Aracaju and 8.5% from Pirambu. Females were larger and heavier than males in both fleets (Aracaju and Pirambu). Inflexion points were observed in the relationships between TL and CL for both sexes (both fleets). The weight-length relationships indicated a negative allometry for both sexes (both fleets). The size at first maturity (CLm) for females was 19.75 mm and 18.94 mm for Aracaju and Pirambu, respectively, and 15.26 mm for males (only for the Aracaju fleet). The reproduction was continuous, with a peak observed in September-October. Except for growth, mortality, distribution, and abundance, both sampling methods allowed for estimating parameters for the population structure and dynamics of F. subtilis. Larger sample sizes would allow for the estimation of growth and mortality parameters when bycatch is included such as the case of the Pirambu fleet. Thus, fishery-dependent data may be used to partially monitor shrimp stocks in Sergipe and other localities where limiting resources are available.