Freshwaterfishery resources in Chinese rivers have been markedly impaired as the results of overfishing,damming,and watershed development.However,little is known about trophic ecology offish assemblages in the rivers ...Freshwaterfishery resources in Chinese rivers have been markedly impaired as the results of overfishing,damming,and watershed development.However,little is known about trophic ecology offish assemblages in the rivers of China.In this study,fishes were collected from an upstream,midstream,and downstream site of the Moyangjiang River,Southern China,to investigate trophic niche structure using stable isotope analysis.We calculated several trophic niche metrics usingδ13C andδ15N ratios of thefish assemblages at each study site.Results showed no significant differences in theδ13C ratios between the pelagic and benthicfish assemblages at each study site.This suggests a homogenous dietary base shared by allfish at each site,likely as the result of continuous water column mixing in this shallow and fast-moving river.The upstreamfish assemblage had the greatest species abundance and trophic diversity.Thefish assemblage at the midstream site displayed the smallest trophic niche space(total area of theδ13C andδ15N bi-plot space)and trophic diversity.The midstream site also showed the most depleted 13C,suggesting a more degraded habitat compared with the other two study sites.Thefish assemblages at the downstream site displayed the greatest basal resource diversity,largest CR,and trophic niche space and trophic diversity.However,thefish assemblage at the downstream site also displayed the lowest species abundance,redundancy,and evenness of trophic spacing.Thesefindings suggest that the trophic niche of thefish assemblage at the downstream site,which received resources from upstreamflow,experienced greater watershed development and greater in situ production,demonstrating positive and negative impacts by anthropogenic activities.Future studies should also gather information onfish production,watershed development,and water quality,to aid in the interpretation of the stable isotope analysis offish trophic niches.展开更多
基金Natural National Science Foundation of China,Grant/Award Number:41376158Bureau of Science and Technology of Guangdong Province,Grant/Award Numbers:2005A20105001,2006B20701001,B200601G02China Agriculture System,Grant/Award Number:CARS-50。
文摘Freshwaterfishery resources in Chinese rivers have been markedly impaired as the results of overfishing,damming,and watershed development.However,little is known about trophic ecology offish assemblages in the rivers of China.In this study,fishes were collected from an upstream,midstream,and downstream site of the Moyangjiang River,Southern China,to investigate trophic niche structure using stable isotope analysis.We calculated several trophic niche metrics usingδ13C andδ15N ratios of thefish assemblages at each study site.Results showed no significant differences in theδ13C ratios between the pelagic and benthicfish assemblages at each study site.This suggests a homogenous dietary base shared by allfish at each site,likely as the result of continuous water column mixing in this shallow and fast-moving river.The upstreamfish assemblage had the greatest species abundance and trophic diversity.Thefish assemblage at the midstream site displayed the smallest trophic niche space(total area of theδ13C andδ15N bi-plot space)and trophic diversity.The midstream site also showed the most depleted 13C,suggesting a more degraded habitat compared with the other two study sites.Thefish assemblages at the downstream site displayed the greatest basal resource diversity,largest CR,and trophic niche space and trophic diversity.However,thefish assemblage at the downstream site also displayed the lowest species abundance,redundancy,and evenness of trophic spacing.Thesefindings suggest that the trophic niche of thefish assemblage at the downstream site,which received resources from upstreamflow,experienced greater watershed development and greater in situ production,demonstrating positive and negative impacts by anthropogenic activities.Future studies should also gather information onfish production,watershed development,and water quality,to aid in the interpretation of the stable isotope analysis offish trophic niches.
