Population dynamics of Gray eel catfish (Plotosus canius Hamilton, 1822) 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 2017 to December 2018. A total amount of 1298 specimens was collected to estimate the total length (TL) and weight (W) of P. canius ranged from 13.3cm to 87.4cm and 28g to 5200g respectively. The length-weight relationship was W=0.006 L2.95 with R2=0.972 for both sexes. The von Bertalanffy growth function parameters were L∞=93.25cm and K=0.28yr-1, hypothetical age at zero length of t0=0.059 year and goodness of the fit of Rn=0.494. The growth performances indices for L∞ and W∞ were computed as Ø'=3.386 and Ø=1.84 respectively. The natural mortality was 0.51yr-1 at average annual water surface temperature as 22°C. The total instantaneous mortality was 1.24yr-1 at CI95% of 1.05–1.42 (r2=0.986). While fishing mortality was 0.73yr-1 and the current exploitation ratio as 0.59. The recruitment was continued throughout the year with one major peak during June-July was 17.20-17.96%. The Beverton-Holt yield per recruit model was analyzed by FiSAT-II, when tc was at 1.443 yr, the Fmax was estimated as 0.6yr-1 and F0.1 was 0.33yr-1. At the age of 0.6 year, Fcurrent was 0.74yr-1 that is beyond the F0.1 that specified the current stock of P. canius of Bangladesh was over-exploited.