Baseline demographic parameters of the Small Indigenous Fish Cabdio morar (Hamilton, 1822) in the Brahmaputra River System

Abstract

Cabdio morar (Hamilton, 1822), an important small indigenous fish of the Brahmaputra River, plays a significant role in small-scale fisheries, yet data on its demographic parameters remain limited. The present study examined the growth, mortality, and exploitation status of C. morar using length–frequency data collected from two major fish landing sites along the Brahmaputra River between October 2024 and September 2025. A total of 648 specimens, ranging from 43 to 144 mm in total length, were analysed. Growth parameters estimated using the von Bertalanffy Growth function indicated an asymptotic length (L∞) of 152.7 mm and a growth coefficient (K) of 0.83 yr −1 . Mortality estimates indicated nearly equal natural mortality (M = 1.47 yr −1 ) and fishing mortality (F = 1.44 yr −1 ), resulting in a current exploitation rate (E curr = 0.49), which was below the estimated maximum exploitation rate (E max = 0.66). Length-structured virtual population analysis indicated that fishing mortality was concentrated mainly in intermediate- to larger-size classes represented in the landings. Overall, the findings suggest that C. morar in the sampled sector of the Brahmaputra River is under moderate exploitation. However, these landing-based results should not be generalised as a river-wide stock assessment without further stratified sampling and fishery-independent surveys.