Stock Assessment model and Management of Carp Fishes in the Gandak river, Gopaganj (Bihar)

Abstract

The Gandak River of Bihar is investigated to estimate the Carp fishes stock showed a inverse relationship between Y/R even in low mortality (M=0.17/year) with first catch age (Tc=0.5 years), however, in case of raised mortality rate (F=0.50/year) resulting in a Y/R of 1068g/year. There Yield per recruit remained constant or exhibited a slight decline beyond this threshold with the current fishing mortality rate exceeding the B/R as F0.1 (0.15/year), FSB40% (0.13/year), FSB50% (0.08/year), and FSB25% (0.24/year). Also, 1 year increase in Tc produced a slight rise in Y/R, whereas further increments in Tc resulted in a reduction of Y/R values. Thus, increase in Tc become necessary to achieve the maximum Y/R is required until an optimal state is reached, considering initial recruitment at a constant M; however, the contemporary fishing mortality level produces only a modest increase in its recent rate of F. These findings indicate the presence of recruitment overfishing at all optimal harvest levels illustrating that Carp fishes in this river necessitate reducing F to numbers below F0.1 and FSB40%, achievable by reduced fishing effort without increased Tc is essential for management and conservation of Carp fishes in the river.