Maternal weight, age, and their interaction have impacts on reproductive outcome and offspring performance in Indian butter catfish, Ompok bimaculatus

Broodfish weight and age are crucial for any fish to produce high-quality gametes and larvae. This study aimed to evaluate the effects of maternal weight, age, and their interaction on reproductive performance, egg quality, and larval quality in Indian butter catfish, Ompok bimaculatus , a potential candidate species for aquaculture diversification in India and many other Asian countries. Two induced spawning experiments were conducted with four weight groups (51.25 ± 5.23 g; 80.75 ± 5.12 g; 120.75 ± 6.18 g; and 159.25 ± 6.99 g) and four age classes (1, 1.5, 2 and 2.5 years), and each age class was divided into two weight groups, small and big. The results of experiment-1 revealed that total fecundity (TF), egg size (ED), and egg weight (EW) increased significantly (p < 0.05), whereas relative fecundity (RF) decreased significantly (p < 0.05) with increasing female weight. Fertilization rate (FR) exhibited no significant difference ( p = 0.384); however, hatching rate (HR) was found significantly higher ( p < 0.001) for the medium-sized (F80 and F120) female groups and showed a significant negative (r = –0.73; p = 0.003) correlation with female weight. Growth and survival of larvae were also found to be significantly ( p < 0.05) higher in the offspring of medium-sized female groups and lowest in the offspring of large-sized (F160) female group. Experiment-2 showed that females in the 1–2-year age group performed better, with the highest stripping response (SR), FR, and HR observed in the 1.5-year age class (weight: 54–89 g). Within the individual age class, the smaller-sized female group showed relatively poor reproductive performance compared to the larger-sized female group, particularly in the 1-year age class. However, no significant differences in SR, FR, and HR were observed between the larger-sized female group (weight: 55.37 ± 4.67 g) of the 1-year age-class and both female groups of the 1.5-year age-class. Interaction effects of maternal age and weight on TF, FR, and HR were insignificant (p > 0.05), but highly significant (p < 0.001) for SR and RF. Overall, the study's findings suggest that, although size-dependent selection of O. bimaculatus can yield good reproductive results, size-age-dependent selection (based on the ‘weight-at-age’ concept), with broodfish weighing 60–120 g and aged 1–2 years, is desirable for the best reproductive outcome.