基于碳、氮稳定同位素分析中华绒螯蟹(Eriocheir sinensis)幼蟹溯河洄游期食物来源变化

DIET SOURCES OF JUVENILE CHINESE MITTEN CRAB(ERIOCHEIR SINENSIS)DURING UPSTREAM MIGRATION INDICATED BY THE CARBON AND NITROGEN STABLE ISOTOPES

中华绒螯蟹(Eriocheir sinensis)是我国重要的渔业捕捞和水产养殖对象,但野生中华绒螯蟹溯河洄游过程中的摄食生态尚不明确。本论文以长江野生中华绒螯蟹为研究对象,沿其洄游路线设置3个采样区域,采集不同发育时期的幼体及其潜在的食物来源等样品。通过对比分析幼体及食源样品的碳、氮稳定同位素特征,对中华绒螯蟹溯河洄游期的食物组成及变化进行探讨。结果发现,从大眼幼体到幼蟹,碳稳定同位素(δ^13C)呈现逐渐变轻的趋势,氮稳定同位素(δ^15N)呈现逐渐变重的趋势。表明中华绒螯蟹从大眼幼体到幼蟹的发育过程中,随着幼体不断向上游江段回溯,食物中陆源物质的比例逐渐增大,食物来源由浮游性食物向底栖性食物转变,且营养级逐渐增高。综合分析证明,在生境多样化、食物来源复杂的河流生态系统中,δ^13C值呈现的是食物来源的区域性和特异性,可以识别中华绒螯蟹洄游过程中的食源变化。δ^15N值虽受到区域氮源以及生物地球化学过程的影响,仍能体现幼体发育过程中营养级的差异。

The diet sources of Chinese mitten crab(Eriocheir sinensis)during their migration are not well-known yet.In this paper,the wild Chinese mitten crab was sampled along their migration route from Changjiang(Yangtze)River estuary to the Zhenjiang section of Changjiang River,and their potential diet sources were collected in three regions.The changes in the diet sources of the crab during their migration were analyzed by comparing the carbon and nitrogen stable isotopes of the crab and their potential diet sources.The results exhibit that theδ^13C values decreased but theδ^15N values increased from megalopa larva to juvenile crab.Changes in theδ^13C andδ15N values of the crab during migration suggested that the proportion of terrigenous carbon sources in their diet increased during the upstream migration,and the diet was changed from pelagic to benthic sources,and the trophic level increased.In conclusion,theδ^13C value exhibited differences in region and species of the diet sources,and was shown able to distinguish variation in the diet sources.Although theδ15N value was affected by the regional nitrogen source and biogeochemical process,it could still reflect the change in the trophic level.