Population dynamics of Gangetic major carps from the Sylhet basin, Bangladesh

Abstract

Length-frequency based population dynamics and stock assessment studies of
Catla catla (Ham.), Labeo rohita (Ham.), L. calbasu (Ham.) and Cirrhina mrigala
(Ham.) were done from the Sylhet basin, Bangladesh using FiSAT software.
Estimated fishing mortality and exploitation values of L. rohita, C. catla and L.
calbasu were much higher than the optimum level of 0.5 and remarkably higher
than Emax values which indicated that their stocks are under heavy fishing
pressure. Mean annual catch of L. rohita, C. catla and L. calbasu were much
higher than their maximum sustainable yield (MSY). The Lc/L and M/K values
also confirm the above conclusion. C. mrigala was under optimum or near
to optimum exploitation in both the years and their computed MSY values were
almost close to their annual catch which indicated that the present level of
fishing effort is optimum. Immediate necessary steps need to be taken for judicious
and sustained exploitation by reducing the present fishing pressure gradually
near to 0.82 for L. rohita, 1.07 for C. catla and 1.28 for L. calbasu. Fishing
pressure and exploitation values for both L. rohita and L. calbasu were lower in
the Sylhet basin as compared to the adjoining Mymensingh basin.