长江上游中华沙鳅食性特征的C、N同位素分析

DIET OF SINIBOTIA SUPERCILIARIS BY STABLE ISOTOPE SIGNATURE FROM THE UPPER REACHES OF THE YANGTZE RIVER

应用C、N稳定同位素技术并结合肠含物分析对我国长江上游特有鱼类中华沙鳅(Sinibotia superciliaris)不同发育阶段食性进行了探究。结果显示:中华沙鳅δ^(13)C、δ^(15)N平均值分别为(–22.48±0.85)‰、(10.09±0.69)‰;不同体长段δ^(13)C(P<0.05,F=2.44)、δ^(15)N(P<0.01,F=6.06)值差异显著,暗示了中华沙鳅在生长发育过程中存在食性转变现象;体长<80 mm的个体主要摄食水生昆虫和藻类,属杂食偏肉食性鱼类;体长>80 mm的个体,其食物以虾类、淡水壳菜和水生昆虫为主,属肉食性鱼类。中华沙鳅营养级位于2.02—2.47,与长江上游多种底栖型鱼类生态位相似;食物竞争可能是导致其摄食强度弱和资源量下降的原因之一。研究结果可为长江上游中华沙鳅野生资源保护提供理论参考。

Sinibotia superciliaris belongs to endemic economic fish in upper reaches of the Yangtze River, and its population decreased sharply in recent years because of overfishing and habitat destroy. In this study, intestinal contents and stable isotope analysis from muscle were examined based on specimens collected in May, August and October of 2009 in upper reaches of the Yangtze River, China. The results showed that the mean values of δ^13 and δ^15 of the S. superciliaris were （-22.48±0.85）‰ and （10.09±0.69）‰, respectively. The significant differences in δ^13 （P〈0.05, F=2.44） and δ^15 （P〈0.01, F=6.06） values were associated with body lengths, suggesting the changes of feeding habit during the growth and development of the S. superciliaris. We observed that small individuals （body length 〈80 mm） fed mainly on algae, aquatic insects and organic detritus based on the most important food item in the intestine contents and that big individuals （body length 〉80 mm） ate mainly, Shrimp, Limnoperna lacustris and aquatic insects. The trophic level of S. superciliaris ranged from 2.02 to 2.47, which was similar to the variety of benthic fishes of the upper reaches of the Yangtze River, suggesting that food competition might cause the population decline. The present results may provide useful information in conservation and sustainable utilization of fish resource as well as aquaculture.