Abstract
The present study investigated the length-weight relationship, population parameters and the instantaneous natural mortality rate of Arius thalassinus from two major landing center of Bangladesh using the FAO-ICLARM Stock Assessment Tools (FiSAT II). A total of 1789 specimens were collected between January 2016 and December 2017. The estimated values of the exponent “b” was ranged from 3.019 (pre-monsoon) to 3.293 (monsoon), indicating an isometric growth pattern of the species with high correlation coefficients (0.904 to 0.927). The equation of length–weight relationship was: W=0.005L3.181. Model parameters of the von Bertalanffy growth equation were: L∞ = 97.60 cm and K = 0.33-1 year. The estimated growth performance index (Ø) was 3.497. The instantaneous natural mortality rate (M) was 0.62-1 year and a high exploitation rate (E) 0.62 (>0.50) showed that this fish is over-exploited in the Bay of Bengal coast of Bangladesh.
 Res. Agric., Livest. Fish.6(3): 439-444, December 2019
Highlights
Arius thalassinus, commonly known as giant catfish under the family Ariidae (Pisces, Siluriformes) is an economically important marine fish species for commercial fishing activities in the Bay of Bengal coast of Bangladesh
The ELEFAN I procedure in FiSAT II was employed to estimate growth parameters (L∞ and K) of the von Bertalanffy growth function (VBGF): Lt= L∞ [1 - exp-K(t- t0)], Where, Lt is the length at age t, L∞ is asymptotic length, K is the growth coefficient, and t0 is the theoretical age of fish at zero length t0 was estimated from the “Analysis of Length-at-Age data” routines
The growth performance index (Ø) for Arius thalassinus was calculated according to the following formula (Pauly and Munro 1984): Ǿ = log K + 2 log L∞ The total instantaneous mortality (Z) was estimated by length converted catch curve method (Pauly 1983)
Summary
Commonly known as giant catfish under the family Ariidae (Pisces, Siluriformes) is an economically important marine fish species for commercial fishing activities in the Bay of Bengal coast of Bangladesh. Knowledge on the stock structure of this species in the Bay of Bengal coast of Bangladesh, needed for management, is unknown. The aim of this study was to establish the key population parameters of Arius thalassinus by presenting the Length-Weight Relationship, estimating the growth parameters (L∞, K & to) and calculating the instantaneous natural mortality rate.
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