Estimation of life history parameters for river catfish Eutropiichthys vacha: insights from multi-models for...

The river catfish, Eutropiichthys vacha is a vital protein source for rural communities and has high commercial value, but understanding its life history and management strategies reveals major inadequacies and ambiguities in the riverine ecosystems. Consequently, this study employs multi-models to analyze the life history parameters of E. vacha in the Ganges River (northwestern Bangladesh) from January to December, 2020. The total length (TL) and body weight (BW) of 362 individuals (male = 170, female = 192) were measured by a measuring board and a digital weighing balance, respectively. The overall sex ratio (male: female) was 1.0: 1.13 and did not oscillate statistically from the standard 1:1 ratio (p > 0.05). The TL varied from 6.7-19.2 cm for males and 6.3-19.0 cm for females. The length-frequency distributions (LFDs) revealed females outnumbered in 8.0-9.99 cm TL whereas males in 7.0-7.99 cm TL. The slope (b) of the length-weight relationship (TL vs. BW) for both sexes (b = 2.87) was substantially lower than isometry, specifying negative allometric growth pattern for E. vacha. Sex-specific relative (K ) and Fulton's (K ) condition analysis revealed better state of well-being of males than females. Only K exhibited significant correlation with both BW and TL, hence making it ideal condition for predicting the fitness of E. vacha in this river. Moreover, the relative weight (W ) suggests an imbalanced habitat for females with higher abundance of predators but suitable for males. The form factor (a ) was 0.0062 and 0.0065, whereas the size at first maturity (L ) and mean natural mortality (M ) were 11.38 and 11.27 cm TL and 1.29 and 1.28 year^-1 for the respective sexes. Besides, the calculated mean optimum catchable length (L ) was 13.58 and 13.09 cm TL for each sex. These findings will be crucial for further studies and to recommend appropriate strategy for the sustainable management of E. vacha in the Ganges River and adjacent watersheds.