Estimation of Growth and Mortality Parameters for Two Penaeid Species of Tanzanian Coastal Waters

Abstract

Assessment of the growth and mortality parameters of Fenneropenaeus indicus and Metapenaeus monoceros was conducted. Samples for the study were collected during two ship surveys conducted in February and June 2011 and from land-based surveys on two sites at Bagamoyo and Nyamisati, which was conducted between February 2011 and December 2012. Lengthbased stock assessment FiSAT II software package was used for assessment. The growth parameters which were asymptotic size (L∞), growth coefficient (K), total (Z) and natural (M) mortality, exploitation rate (E) and recruitment pattern were estimated. The results of analysis indicate that asymptotic size (L∞) for F. indicus was 44.1 mm CL for zone 1, zone 2 and Bagamoyo while Nyamisati was 48.3 mm CL. The growth coefficient (K) was 0.42, 0.83, 0.3 and 0.65 per year for zone 1, zone 2, Bagamoyo and Nyamisati respectively. The natural mortality (M) value was low in Bagamoyo and high in zone 2 while exploitation rate (E) and was high at Nyamisati area and low at Bagamoyo site. The study observed high exploitation levels on the two land-based sites (Bagamoyo and Nyamisati) despite the existing moratorium on prawn commercial fishing activities since 2008 hence seasonal closure for artisanal fishers was recommended.