Trophic Niche of Four Oxynoemacheilus Species (Teleostei: Nemacheilidae) in the Different River Basins (Western Türkiye) during the spring

Abstract

Abstract—: This study focused on exploring the food utilization strategies and spring diets of four Oxynoemacheilus species inhabiting different river basins: O. anatolicus, O. eliasi, O. simavicus, and O. theophilii. Our goal was to fill the gaps in the knowledge of the feeding ecology of these small-bodied and non-commercial species, since surprisingly little is known of the properties of their ecological niche. The specimens of each species were collected by electrofishing from the tributaries of three different river basins (Burdur, Küçük Menderes, and Susurluk) in Türkiye. The vacuity index (%VI), represented by low values for each fish species (2.3–8.0), was a mark of high feeding density. Aquatic insects were the main food item in the spring diets of these four nemacheilid species, and they all exhibited generalist feeding habits. Because each species fed heavily on Diptera, niche breadth values (BA) were low (0.01–0.08). Among these four species belonging to the same genus, feeding was closely related to river basin characteristics of the streams and different prey groups possible for different environments. Oxynoemacheilus simavicus and O. theophilii, sympatric species that inhabit the same stream, consumed similar food items in similar proportions, whereas O. anatolicus and O. eliasi, inhabiting different locations, gravitated towards other food types.