Length-Weight, Length-Length relationships and condition factor of the endangered yellowtail catfish Pangasius pangasius collected from the Meghna River Estuary, Bangladesh

The current study was conducted to assess the length-weight relationship (LWR), length-length relationship (LLR), and condition factor of the yellowtail catfish Pangasius pangasius at its juvenile and matured stages. A total of 274 juvenile (8.80-20.20 cm) and 38 (68.50-105.90 cm) matured individuals were collected from the Meghna River Estuary (MRE) in Bangladesh from March to December 2020. The total length (TL) and standard length (SL) of collected samples were measured through digital slide calipers (for juvenile) and measurement tape (for adults). Individual fish weight (W) was determined using a digital balance. The length-frequency distribution of P. pangasius showed unimodal for the juvenile stage and bimodal for adult stages. The regression coefficient ‘b’ obtained from LWR was recorded as 2.25 for juveniles and 3.15 for adults, with a significant positive correlation (r = 0.88 and 0.96, respectively, p <0.01). Highly positive relationships were observed between total length (TL) and standard length (SL) of the species at both juvenile and adult stages (r = 0.96 and 0.98, respectively, p <0.01), recording regression equations as TL = 0.67 + 1.21 SL and TL = 11.46 + 0.99 SL, respectively. The regression analysis of all LWR and LLR were significant (p <0.01). Fulton’s condition factor was found lower at the juvenile stage (0.81±0.21) and higher at the adult stage (1.21±0.14). However, this work form provides the first attempt to document the growth pattern of juvenile and adult P. pangasius from the MRE, which might be useful for the policymakers to make effective management plans to conserve the natural stock of the species.