Seasonal and environmental changes in the diet of Awaous tajasica (Gobiiformes: Oxudercidae) in a threatened Neotropical freshwater ecosystem

Context Environmental and seasonal changes can modulate the trophic niche breadth of Neotropical fish. Aims We evaluated the diet and trophic niche breadth of Awaous tajasica in Neotropical lotic and lentic environments in the lower portion of the Doce River Basin, south-eastern, Brazil. Methods Fish were captured at nine sampling sites in two environments (channel of the Doce River and lakes), in the dry and rainy seasons. Stomach contents were assessed using the volumetric method. Key results On the basis of our feedings, we classified A. tajasica as omnivorous. In lotic environments, the trophic niche breadth was narrow and composed mainly of aquatic insects during the dry season. In the rainy season, the incorporation of terrestrial invertebrates into the diet resulted in the expansion of the trophic niche. In lentic environments, we found zooplankton as the main food component in the diet of the populations. However, seasonal changes in diet and niche breadth were not detected in these environments. Conclusions We concluded that seasonality was a determining factor in the diet composition and trophic niche breadth of the population in lotic environments. Implications Our findings are essential for developing species conservation and management strategies in heavily affected watersheds.