Estimation of growth and mortality parameters of hilsa Tenualosa ilisha (Ham.) population in the Meghna river of Bangladesh

Abstract

Hilsa (Tenualosa ilisha) is an anadromus species constituting an important exploited fishery in Bangladesh. Its essential population characters viz; the growth and mortality were studied using 5,003 specimens from the Meghna river. The asymptotic length was L_ = 57 cm, curvature parameter was K = 0.66 yr1 and the initial time taken to grow was to = 0.50 yr. The semi-higher index of its K value (0.66 yr1) indicates that the hilsa has a moderately longer life span. The smallest length at first capture (L) of hilsa was 3.65 cm and length of larvae at the day of birth was 1.03 mm. Minimum age of hilsa entering the fishery (Tr) and the first capture age (Tc) were 0.58 and 0.60 yr respectively i. e. catching of juvenile hilsa starts after 36.5 days of recruitment. Hilsa population is presumed to be suffering from natural and fishing mortality since the age at recruitment is affected by recruitment over fishing. The total mortality (Z) was 2.03 yr1 and thus it was found that 13.13 % T. ilisha survives only in the Meghna river. The natural mortality (M) was 0.89 yr1 and the fishing mortality (F) was 1.14 yr1. The exploitation rate (E) of hilsa was 0.56, indicating a trend towards overexploitation