Crescimento e mortalidade do camarão-branco Litopenaeus schmitti capturado no Nordeste do Brasil

Abstract

Shrimp fishing has great economic, social and cultural importance in the Northeast region of Brazil. The shrimp Litopenaeus schmitti (white shrimp or Vila Franca) is one of the fisheries resources with the greatest prominence and catch values in marine fisheries. Therefore, this study aimed to analyze the growth and mortality of white shrimp in the cities of Lucena (PB) and Sirinhaém (PE). These analyzes were carried out for males, selective and grouped sexes, from a database for animals captured from August 2011 to July 2012 in Sirinhaém and between December 2016 and November 2017 in Lucena. Biometric relationships between measurements of length (cephalothorax and total) and weight were performed from equations fitted by linear and nonlinear regressions based on the squared data method. A modal progression analysis uses an ELEFAN routine from the Fisat program to estimate the growth parameters L[infinity] (asymptotic growth of the cephalothorax), k (growth coefficient), and [Phi] (growth performance index) in the von Bertalanffy formula and parameters of total mortality (Z), natural (M) and by fishing (F) in addition to the exploitation rate (E), size of first catch (Lc) and longevity (Long). In both locations there was a significant difference (p <0.05) in the relation of cephalothorax and total length for males and females, and for sexes grouped in the both locations. Both sexes exhibited negative allometric growth (b <1), with greater growth in total length than the cephalothorax. The relationship between weight and total length showed positive allometry (b> 3) in the Lucena region, resulting in greater weight gain than in length. In Sirinhaém, however, the opposite was observed for this relationship, indicated by the negative allometry value (b <3). The estimated values of the growth parameters for separate and grouped sexes were lower for the shrimp population in the Lucena region, however, the parameters of Z and E were higher in Sirinhaém. This fact may be related to the beach trawl fishing in the Lucena region, while in Sirinhaém fishing takes place with motorized trawl off the the coast. However, females were larger (cephalothorax and total length) in both locations and heavier than males. Reproductive activity is likely caused this result, due to the greater body area occupied by the ovaries and ovarian weight during their maturation. The results of this study can contribute to the stock assessment and sustainability of fishing for this species in the Northeast region.