Feeding Strategies and Trophic Level of Chirocentrus dorab (Forsskål, 1775): A Seasonal and Ontogenetic Analysis

Abstract

This study investigates the feeding dynamics and trophic role of Chirocentrus dorab along the southern coast of Karnataka to support ecosystem-based fisheries management. A total of 381 specimens collected between October 2023 and September 2024 were examined using stomach content analysis, Index of Relative Importance (IRI), Quotient Index (QI), and multivariate statistical tools including MDS and SIMPER. Among the analysed specimens, 346 contained food, while 9.18% had empty stomachs, with juveniles showing a higher Empty Stomach Ratio (ESR) (11.35%) than adults (7.14%). ESR was lowest during post-monsoon (3.77%) and highest during monsoon (25.71%), whereas the Repletion Index (RI) peaked post-monsoon (0.0542) and was lowest in monsoon (0.0124). Teleosts were the dominant prey (%QI = 84.49; %IRI = 74.19), followed by crustaceans (%IRI = 21.05) and mollusks (%IRI = 4.88). The estimated trophic level was 4.2, with juveniles at 3.8 and adults at 4.25, indicating a clear ontogenetic dietary shift. The Omnivory Index (OI) was 0.33, higher in adults (0.39) than juveniles (0.15). Seasonal variation significantly influenced diet composition, with species richness highest in January (S = 8). MDS revealed distinct seasonal feeding patterns, and SIMPER analysis showed monsoon diets dominated by shrimps and mackerel, whereas post-monsoon and pre-monsoon diets were characterized by sardines and anchovies. Overall, the results highlight the strong dependence of juveniles on crustaceans and the dominance of pelagic teleosts in adult diets, providing essential inputs for marine ecosystem modelling and sustainable management of wolf-herring resources in the southeast Arabian Sea.