(1) College of Fisheries, Huazhong Agricultural University, Wuhan 430070, China
; (2) States Key of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
This study was undertaken to assess the trophic niches and niche widths between two freshwater shrimps, Macrobrachium nipponensis and Exopalaemon modestus, from the Yangtze River-connected lakes-Dongting lake and Poyang lake-using stable carbon and nitrogen isotope analysis. The overall aim was to provide the information valuable for evaluation of trophic relationships and for protection of natural resources. Results showed significant differences in δ13C values between M. nipponensis and E. modestus, but no difference in δ15N values between two species. Meanwhile, differences in isotopic variations of shrimps were found between lakes which had differences in nutrient level and in hydrology. The range of δ13C signatures in M. nipponensis was greater than those of E. modestus and mainly distributed from -25.0‰ to -23.0‰, indicating that M. nipponensis fed on more food sources but preferred a certain one. There was a large overlap of trophic niches between the two species. This result indicated that food consumed were nearly the same for both species, implying similar trophic positions and strong inter-composition. In the Poyang Lake, M. nipponensis had a trophic niche and niche width larger than E. modestus. However, there were opposite observations in the Dongting Lake due to variations of sampling habitats and the degree of human disturbances.