Dietary Niche Partitioning and Trophic Significance of Insect and Crustacean Prey in Silver Catfish (Chrysichthys nigridigitatus)

The feeding ecology of Chrysichthys nigrodigitatus was studied in the Cross River Estuary, Nigeria, to evaluate its trophic dynamics and resource use across size classes, sexes, and seasons. Fish samples (n = 230) were collected from artisanal landings between March 2023 and February 2024, and stomach contents were analyzed using the index of relative importance (IRI), Shannon–Wiener diversity index, and Schoener’s index. Results showed that crustaceans (54.2% IRI) and insects (39.7% IRI) were the dominant prey categories, with seasonal variation in prey composition: crustaceans contributed more in the dry season (62.4% IRI), while insects were dominant in the wet season (47.8% IRI). Length–frequency analysis indicated a broad representation of size classes, with sub-adults showing the highest dietary niche breadth (H′ = 2.18) compared to juveniles (H′ = 1.67) and adults (H′ = 1.54). Schoener’s index revealed moderate dietary overlap among size classes (0.54–0.72) and high overlap between sexes (0.69). These findings suggest that C. nigrodigitatus is an opportunistic feeder with flexible dietary strategies, relying heavily on benthic invertebrates. The study concludes that conservation of benthic habitats is critical for sustaining this economically important species and recommends the incorporation of benthic habitat monitoring into estuarine fisheries management programs.