Reproductive biology of Gagora catfish (Arius gagora) at Meghna river system, Kushiara River, Bangladesh

The gagora catfish, Arius gagora is a species of Ariidae family normally exist in estuaries and tidal rivers of Bangladesh and India. In the present study, the reproductive biology of A. gagora was assessed in Meghna River system at Kushiara River. Length-weight relationship was found strongly correlated for male (r^2 = 0.98), female (r^2 = 0.97) and combined sex (r^2 = 0.81), respectively. Chi-square tests revealed no significant difference between sex ratios round the year and not deviated from the expected value of 1:1 (χ^2 = 5.57) and the critical chi-square value calculated was 143.25. The fecundity found to be ranged from 43333.12±829.83 to 53948.81±1743.28 in April to August. The relationship of fecundity with ovary weight (r^2 = 0.79), ovary length (r^2 = 0.88), total length (r^2 = 0.85) and total weight (r^2 = 0.68) were found positively correlated. Monthly study of gonadosomatic index (GSI) revealed that the breeding season for this fish species may be between July to August with a single peak spawning month in August. Size at sexual maturity was estimated as 30.01 cm total length. Fulton’s condition factor (K) value varied in both males and females and indicates that the overall health condition of both the male and female were excellent. Breeding season was found significantly correlated with rainfall, but not with other biological, meteorological, and hydrological parameters. Ovarian development of A. gagora was assessed macroscopically and three broad gonad developmental stages were identified. Maturity was specified based on the presence of green egg in the peritoneal cavity. These findings should benefit and improve the sustainable management and conservation of this species both in Bangladesh and its bordering countries.