Growth, mortality and exploitation of male and female populations of Macrohrachium rosenhergii (de Man) in the Vembanad lake, India

Abstract

Based on length composition of commercial landings of Macrobrachium rosenhergii (de Man) of the Vembanad lake, growth parameters L_ and K were estimated separately for male and female populations using ELEFAN I and modal progression analysis. Growth equations of the two populations based on the growth parameters computed by integrated method can be expressed as follows: Males : Lt=454.89 (l-exp-0.6780(t-0.1580) Females : Lt=297.36 (1-exp- 1.3660 (t-0.2260). Total mortality (Z), natural mortality (M) and fishing mortality (F) were worked out separately and results showed that averages of both total mortality and natural mortality were found to be high in females when compared to that of males. Similarly, fishing mortality coefficients and exploitation rate were also found to be high in females when compared to their male counterpart. Length converted cohort analysis showed that prawns below 100 mm are not vulnerable to exploitation in males against 80 mm in females. Fishing mortality in males was found to be high in prawns of 230-290 mm TL while in female it was invariably high in prawns of size 210-230 mm TL.