Trophic Niche Width and Overlap of Three Benthic Living Fish Species in Poyang Lake: a Stable Isotope Approach

An occupied niche space implies resource use, and understanding the factors that lead to change in trophic niches is vital to assess food web structures. Quantifying niches and niche overlaps are important to assess interspecies resource partitioning and competition. In this study, stable carbon and nitrogen isotopes were used to characterize trophic niche width of and niche overlap among three commercially-important benthic-living fish (Carassius auratus, Pelteobagrus fulvidraco, and Silurus asotus) collected from northern and southern Poyang Lake. The separation of snails and mussels on the delta C-13 at southern part indicating the integration of terrestrial derived organic carbon, which led to larger trophic niche widths of fish in the south. The delta N-15 ratios of fishes were significantly higher in the northern Lake than in the southern part. Furthermore, the trophic overlaps were higher in the south than in the north. Trophic niche width of C. auratus was the smallest as their food sources were easy to acquire, and consumers tended to specialize and narrow their trophic niches when food resource is abundant. S. asotus, a predator species, was short of animal food sources due to heavy fishing pressure. Therefore, its diet broadened, and the trophic niche width was the largest.