Growth and stock assessment of Macrobrachium amazonicum (Decapoda:Palaemonidae) in an estuary of northeast Pará, Brasil

Abstract

In this study, growth and mortality rates, and maximum sustainable yield of Macrobrachium amazonicum (Heller, 1862), in Northeastern Pará, were estimated. Monthly samples at two sites of the Bragança Peninsula (Flexal and Curral Velho) were taken during August 2008 í  July 2009. Bhattacharya method showed a constant biomass increment in this population, indicating a constant reproductive activity. Females showed two clear annual recruitment peaks, whereas males only showed one. To reduce errors in the calculation of growth parameters, different methodologies were employed. Mean growth parameters for both sexes were: annual growth rate (K = 0.31 year^-1); asymptotic maximum length (L∞ = 47.83 mm); growth curve oscillation (C = 0.36) and winter point (WP = 0.41). Growth performance (Φ´) was 2.8 and the estimated age was four years. For both sexes grouped, mean total mortality (Z), natural mortality (M) and fishing mortality (F) was 1.97; 0.73 and 1.52, respectively. The maximum sustainable yield (E_max = 0.586) with values very close to current exploitation rate (E = 0.574) indicates that stocks of M. amazonicum in the study area show signs of overexploitation, denoting that urgent fisheries management actions for this species are needed.