Research Article: Population dynamics of Gray eel catfish (Plotosus canius Hamilton, ۱۸۲۲) at mangrove estuary in Bangladesh

Present study emphasizing the population dynamics parameters of Gray eel catfish (Plotosus canius) that was scrutinized based on monthly length frequency data collected from mangrove estuary, Bangladesh from January ۲۰۱۷ to December ۲۰۱۸. A total amount of ۱۲۹۸ specimens was collected to estimate the total length (TL) and weight (W) of P. canius ranged from ۱۳.۳cm to ۸۷.۴cm and ۲۸g to ۵۲۰۰g respectively. The length-weight relationship was W=۰.۰۰۶ L۲.۹۵ with R۲=۰.۹۷۲ for both sexes. The von Bertalanffy growth function parameters were L∞=۹۳.۲۵cm and K=۰.۲۸yr-۱, hypothetical age at zero length of t۰=۰.۰۵۹ year and goodness of the fit of Rn=۰.۴۹۴. The growth performances indices for L∞ and W∞ were computed as Ø'=۳.۳۸۶ and Ø=۱.۸۴ respectively. The natural mortality was ۰.۵۱yr-۱ at average annual water surface temperature as ۲۲°C. The total instantaneous mortality was ۱.۲۴yr-۱ at CI۹۵% of ۱.۰۵–۱.۴۲ (r۲=۰.۹۸۶). While fishing mortality was ۰.۷۳yr-۱ and the current exploitation ratio as ۰.۵۹. The recruitment was continued throughout the year with one major peak during June-July was ۱۷.۲۰-۱۷.۹۶%. The Beverton-Holt yield per recruit model was analyzed by FiSAT-II, when tc was at ۱.۴۴۳ yr, the Fmax was estimated as ۰.۶yr-۱ and F۰.۱ was ۰.۳۳yr-۱. At the age of ۰.۶ year, Fcurrent was ۰.۷۴yr-۱ that is beyond the F۰.۱ that specified the current stock of P. canius of Bangladesh was over-exploited.

Keywords:

Plotosus canius , Mangrove estuary , Asymptotic length , Growth , Mortality , Bangladesh