应用稳定同位素技术对南黄海两种鳀科鱼类食物竞争的研究

Diet Competition between Two Anchovies Fishes In the Southern Yellow Sea with Stable Isotope Techniques

根据2005年4～5月在黄海海域进行的春季定点底拖网调查，采用稳定同位素技术和聚类分析方法，研究南黄海低营养层次鱼类中的代表性种类，鳀鱼（Engraulis ja ponicus）和赤鼻稜鳀（Thrissa kammalensis）摄食的食物组成、相似指数及二者对食物竞争的激烈程度．结果显示：1）〉900μm浮游动物、500～900μm浮游动物和仔稚鱼3种饵料为南黄海鳀鱼和赤鼻稜鳗的主要摄食对象；2）二者所摄食的食物组成高度相似，相似指数为65．97％；3）在81～100mm叉长组内的食物平均重叠系数为97．95％，101～105mm内为77．96％，116～120mm内为7．28％，表明南黄海鳀鱼与赤鼻稜鳀在一定环境下对食物可能存在激烈的竞争．

Stable nitrogen isotope ratios （δ^15 N） are commonly used to represent the trophic structure of aquatic systems. In this study, we mainly focus on the stable carbon （^13 C/^12C） and nitrogen isotope （^15 N/^14 N） ratios of anchovy, madura anchovy and their potential food sources, such as zooplankton, Euphausia pacifica, Leptochela gracilis, fish larvae and juvenile fish, Sepiola birostrata, Acetes chinensis and so on in the southern Yellow Sea in order to acknowledge the diet competition of anchovy and madura anchovy of two representative anchovies fishes. The principle underlying this approach is that in marine systems, stable isotope ratios of nitrogen and carbon in consumers reflect those of their prey in a predictable manner, application of δ^13 C and δ^15 N in dietary study depends upon the differentiation in the isotopic composition of various food sources and adequately estimating the amount of biomagnification for the species. Based on the bottom trawl surveys in the southern Yellow Sea during the spawning season of Spring in 2005. The δ^13 C and δ^15 N values of anchovy and madura ancho vy indicated that〉900μm zooplankton, 500-900μm zooplankton and fish larvae and juvenile fish were the important dietary component for them; the food compositions of two species similarity significantly from each other, the degree of diet similarity is 65.97%; the mean degree of diet overlap was 97.95% between 81-100 mm fork length class, 77.96% between 101-120 mm and 7.28% between 115-120 mm, the result indicated that diet competition of anchovy and madura anchovy in the southern Yellow Sea were significantly when they lived in the corresponding condition.