Growth and mortality analyses of the white shrimp Penaeus schmitti (Decapoda: Penaeidae) in Sepetiba Bay, Brazil: An exploited data-deficient species

Abstract

Penaeus schmitti is fisheries resource explored throughout the area where it occurs and is one of the most important penaeid in terms of fishery biomass in Brazil. The current conservation state of P. schmitti in Brazil is worrisome because inserted in the category of Insufficient Data in the Red book of Crustaceans of Brazil. The goals of this study were to estimate growth and mortality rates of P. schmitti in Sepetiba Bay, Rio de Janeiro State, southeastern Brazil, and to assess the effect of fishing on the population. Monthly samples were collected during one year through regional artisanal fishery. Growth was assessed through modal analysis according to von Bertalanffy growth function (VBGF). Instantaneous mortality rates Z (total), M (natural), F (fishing) and the exploitation rates (E) were estimated. Total mortality (Z) was estimated by length-converted catch curves and M was based on parameters of the VBGF. Growth parameters differed significantly between sexes and a single curve could not be applied to both sexes. Females of P. schmitti, were larger and grow faster (high k value) but were less abundant than males. Instantaneous mortality rates were similar for males and females. Females were vulnerable to fishing activities at three months of age, males at four months of age. The exploitation rate of the species was greater than 50%, highlighting a possible overfishing of the species. Limiting access to nursery areas of juveniles would be a good strategy for stock recovery.