Longitudinal habitat gradient affects diet and body condition of riverine fish: A case study of Pelteobagrus catfishes in the Three Gorges Reservoir, China

Abstract

To understand how riverine fish respond to longitudinally different habitats created by impoundment, we selected three congeneric yellow catfish species (Pelteobagrus spp.) as a model system to assess changes in diet, prey selectivity, and body condition among the lotic, transitional, and lentic habitats along the Three Gorges Reservoir. Our results add to previous findings highlighting a shift in fish diets from diverse zoobenthos to shrimp-dominated as the river becomes lentic by showing spatial segregation in the size of shrimp prey consumed. Relative to the available shrimp populations, catfish populations selected smaller shrimp in the upper (lotic) section and larger shrimp in the middle (transitional) and lower (lentic) sections. Complementary body condition indices exhibited a consistent spatial pattern, where populations in the lotic zone were healthier than those in the transitional and lentic zones. This pattern seems to result from a greater nutrient value of zoobenthos, the dominant food in the lotic zone, relative to shrimps. Our results suggest that these generalist fish species have adapted to the spatial habitat gradient and maintained their populations, but the impoundment has deeply influenced their energy acquisition and allocation.