Feeding ecology, trophic interaction and resource partitioning among four omnivorous finfish species of a tropical Estuary

A crucial aspect of sustainable resource management is understanding the trophic interactions amongst fish in the estuarine ecosystem. The goal of this study was to look into the food preferences, feeding strategies, trophic partitioning, as well as dietary overlap among four omnivorous species that live in the Cochin Estuary: Mugil cephalus (n = 73), Planiliza parsia (n = 35), Planiliza planiceps (n = 65) and Chanos chanos (n = 55) through the analyses of gut-content. Index of relative importance demonstrated that prey items in Mugil cephalus and Planiliza planiceps guts were dominated by Bacillariophyceae whereas in Planiliza parsia and Chanos chanos guts were dominated by Myxophyceae. The highest diet value (7.5) was recorded in Chanos chanos, while the lowest was recorded in Mugil cephalus (5.69). The highest niche breadth value (0.77) was recorded in Planiliza planiceps while the lowest value was recorded in Planiliza parsia (0.52). Pianka's overlap, evaluated with the help of null models structured by Ecosim 7.0, showed remarkable niche overlap between Mugil cephalus and Planiliza planiceps (0-0.92, P < 0.001), between Planiliza planiceps and Planiliza parsia ( 0-0.77, P < 0.05) and between Mugil cephalus and Planiliza parsia ( 0-0.7, P < 0.05). The fish's trophic niche width, along with prey-specific abundance confirmed that they are generalist feeders. The present results differed from the general hypothesis related to the omnivorous species and concluded that these four omnivorous species live in the same niche zones of the Cochin Estuary with no interspecific conflict. This work provides the first information about feeding habits, trophic ecology and trophic interactions of all examined species(Planiliza parsia, Planiliza planiceps, Mugil cephalus and Chanos chanos) from Cochin Estuary. The result of this work differs from the hypothesis related to omnivorous fishes and concludes that these four omnivorous species live in the same niche zones of the Cochin Estuary with no interspecific conflict. This work will help to give light to the trophic interaction of this species and helps to formulate sustainable resource management.