长江口斑尾刺虾虎鱼的摄食习性

Feeding habits of Acanthogobius ommaturus in the Yangtze Estuary

2014年6月至2015年5月,在长江口东旺沙、东风西沙和青草沙潮间带水域隔月进行插网作业,共采集到459尾斑尾刺虾虎鱼（Acanthogobius ommaturus）样品,分析其胃含物。结果表明,斑尾刺虾虎鱼共摄食12类37种生物,主要摄食虾类,其次是鱼类、蟹类等。其饵料生物组成随季节和体长的不同而有所变化,除四季均大量摄食虾类以外,春季还摄食糠虾类和蟹类,夏季还摄食鱼类,冬季还摄食糠虾类;体长〈70 mm的斑尾刺虾虎鱼主要以幼鱼为食,同时还摄食大量的糠虾类和磷虾类,体长70~189 mm的个体主要摄食虾类和鱼类,体长〉189 mm的个体主要以鱼类为食。聚类分析结果表明,斑尾刺虾虎鱼秋季的饵料生物组成与春、夏、冬季相比,存在较大差异;体长〈70 mm的斑尾刺虾虎鱼食物组成与体长≥70 mm相比,存在较大差异。斑尾刺虾虎鱼的摄食强度也有显著的季节和体长变化,Kruskal-Wallis非参数秩检验结果表明,不同季节组和体长组平均胃饱满系数均差异显著（P〈0.01）;列联表检验结果表明,不同季节斑尾刺虾虎鱼的空胃率不存在显著差异（P〉0.05）,不同体长组空胃率差异显著（P〈0.01）。通过计算Spearman等级相关系数得到饵料生物体长与斑尾刺虾虎鱼体长之间呈显著的正相关（rs=0.263,P〈0.01）。此外,摄食饵料平均重量和个数随着斑尾刺虾虎鱼体长的增大而增大,符合“最佳摄食理论”。因此,斑尾刺虾虎鱼的摄食习性不仅与环境中饵料生物丰度有关,也与其自身生长发育有关。

The Yangtze Estuary is the largest estuary in the Pacific West Bank and is an important spawning ground, feeding ground, wintering ground, and migration route for fish.Acanthogobius ommaturus has potential economic value, but few studies have been performed on this species. A feeding study is important to understand the biology and ecology of a fish species, as well as the fish community and entire ecosystem structure and function. Domestic and foreign scholars have conducted some studies on feeding ofA. ommaturus, but no study has been conducted in the Yangtze Estuary. The feeding habits ofA. ommaturuswere investigated in 459 individuals collected bimonthly from the Yangtze Estuary （June 2014 to May 2015） by analyzing their stomach contents. The prey items included 12 groups and 37 prey species dominated by decapods. The prey groups included Mysidacea, fish, and crabs, and the advantage prey species wereExopalaemon carinicauda andMysidacea sp. The prey items were similar to those reported previously from Jiaozhou Bay, Bohai Sea, Laizhou Bay, and the Huanghe Delta; however, the ad-vantage prey species were not the same. Thus, the habitat of the prey determined the dietary composition ofA. ommaturus. The dietary composition of prey consumed varied seasonally. Decapods were the most important group throughout the year, whereas mysidacea and crabs were predominant in spring, fish were predominant in summer, and mysidacea were eaten mostly during winter. The seasonal variation in prey items was closely related to the life cycle of the fish. Dietary composition also had clear ontogenetic variations; fish 〈70 mm standard length （SL） consumed juvenile fish, mysidacea, and euphausiacea, those 70–189 mm SL consumed shrimp and fish, and those 〉189 mm SL mainly consumed fish. The species and size of prey items were highly significantly dif-ferent among body lengths. A cluster analysis for season employing the Euclidean distance index revealed one diet group in autumn, and another for spring, summer, and winter. The cluster analysis for ontogeny revealed a diet group 〈70 mm SL and another group≥ 70 mm SL. Feeding intensity also varied seasonally and during develop-ment. The Kruskal–Wallis nonparametric rank test and a contingency table revealed that the mean stomach full-ness index ofA. ommaturus varied seasonally （P〈0.01）. The percentage of empty stomachs did not differ among seasons （P〉0.05）, but the mean stomach fullness index and percentage of empty stomachs varied during develop-ment （P〈0.01）. The feeding intensity of fish was lower during winter than that during autumn, which may be re-lated to the reduced number of prey and temperature. Feeding intensity was higher during summer than that during spring, which may be related to larger fish size. A strong positive correlation was found between body length of prey and that ofA. ommaturus（rs=0.263,P〈0.01）. Predation byA. ommaturusincreased gradually as mouth parts developed with growth. Moreover, mean prey weight and mean prey number increased with increasing body length, which is consistent with optimal foraging theory.