蒙古鲌食性转变的稳定性同位素研究

摘要

During the process of maturity, a clear change occurred in using food resources with the development of fishes. There is usually an obvious niche shift in different ontogenetic stages, and the living environment and food groups would be converted with the increase of body size. Traditionally the method which is used for food shift is to analyze the contents in stomach and intestines, however, it could not completely show the location of fishes in food web as well as food source. In recent years stable isotopic way has been widely used to research food types of animals in different environments. The stable carbon isotope composition of consumers is able to show where the foods derive from, while the nitrogen isotope composition can show the position of trophic levels in food web. Mongolian culter( Erythroulter mongolicus mongolicus), which is one of the main economic fishes in Xiaojiang River after the Three-Gorges Reservoir accumulated water, plays an important role in aquatic ecosystem. The diet shift of Mongolian culter in various ontogenetic stages has a deep impact on the aquatic ecosystem. Therefore, based on the stable isotope analysis, combined with the identification of contents in stomach and intestines, we herein discussed the Mongolian culter food groups from Quma town and Huangshi town along the Xiaojiang River region so as to provide a theoretic basis for the management of Xiaojiang fishery resources and enhancement and releasing. Our results indicate that the 813C and δ15N values of small Mongolian culter whose length is less than 200 mm are( -24.50%o ± 1. 15%o) and (12. 17%o ±1. 54%o) respectively,diey are carnivorously omnivorous with 2.9 of trophic level; those big ones of more than 200 mm in length are( -23. 87%o ± 1. 12%o) and (13.54%o ± 1.12%o) respectively, their trophic level is 3. 3 and diet type is carnivorous. The fact that the 8MC and 8I5N values of large Mongolian culter are significantly higher than that of small ones(P <0.01), showing that a diet transfer took place during their growth,but there is an overlap of isotope values between large and small Mongolian culter for their sharing the foods from the same source. This study helps to predict the "top-down effect" caused by the enhancement and releasing of fishes and a variety of fisheries resources management activities such as fishery capture in Xiaojiang River region.%采用稳定性同位素分析并结合胃肠内容物鉴定,探讨了小江水域渠马镇至黄石镇段蒙古鲌食物组成.结果显示,体长＜200 mm的小个体蒙古鲌δ13C、δ15N值分别为(- 24.50‰±1.15‰)、(12.17‰±1.54‰),食性类型为杂食性偏肉食性,营养级为2.9；体长＞200 mm的大个体蒙古鲌δ13C、δ15N值分别为(- 23.87‰±1.12‰)、(13.54‰±1.12‰),食性类型为肉食性,营养级为3.3；大个体蒙古鲌δ13C、δ15N值极显著大于小个体蒙古鲌(P＜0.01),表明蒙古鲌在生长发育过程中发生了食性转变,但部分大个体蒙古鲌和小个体蒙古鲌由于食物来源相同而出现了同位素值重叠现象.