池塘养殖匙吻鲟与鳙胃肠道饵料生物的比较

通过对同一试验池中匙吻鲟（Polyodon spathala）和鳙（Aristichthys nobilis）胃肠道内含物的连续3次分析，揭示他们滤食的天然饵料生物组成及差异。首先根据物种鉴定结果对2种鱼的胃肠道内饵料生物组成进行了UPGMA聚类分析，结果显示:相同采样时间同一池塘内2种鱼饵料生物组成存在差异，分别聚为不同的分枝；分析匙吻鲟和鳙胃肠道内饵料生物种类时还发现不同采样时间前者枝角类和桡足类种类数均多于后者。同时对2种鱼胃肠道内各饵料生物的生物量进行分析，结果显示:当大型饵料生物充足时，枝角类和桡足类的生物量在2种鱼胃肠道内没有显著差异（P0.05）；当大型饵料生物减少时，匙吻鲟摄食强度减小，但其枝角类和桡足类的生物量仍显著较大（P0.05）；当大型饵料生物消失后，轮虫生物量在匙吻鲟胃肠道内显著增加 （P0.05）；相比较，鳙在各采样期则主要滤食较小型的浮游动物和浮游植物。另外，当动物性饵料减少后，匙吻鲟和鳙均通过大量滤食植物絮团来补充能量。综上，同一试验池养殖的匙吻鲟和鳙存在摄食竞争压力，该压力的大小与环境中大型饵料生物的丰富度密切相关。  

COMPARISON OF FOOD ORGANISMS IN GASTROINTESTINAL TRACT OF PADDLEFISH (POLYODON SPATHALA) AND BIGHEAD CARP (ARISTICHTHYS NOBILIS) FROM POND

Three consecutive analysis of gastrointestinal contents of paddlefish (Polyodon spathala) and bighead carp (Aristichthys nobilis) were conducted. To find out their natural food organisms and difference, the fishes were cultured in the same farming pond. The paddlefish and bighead carp were large size fingerlings propagated in this year from the same trail fishery. Two repeated ponds were prepared, and 14 paddlefishes together with 14 bighead carps were included in each pond. All fishes were fed with natural food in the ponds during the whole trail. Each three replicate samples of gastrointestinal tracts of two species of fishes were collected once for three times from the start of the experiment (3d, 11d and 19d). The identification of food organism was carried out with microscope in the lab. Firstly, the unweighted pair group method with arithmetic mean (UPGMA) cluster analysis was performed on the basis of food organisms identification in gastrointestinal tract of two fish species. The results showed the composition of food organisms was different in two fish species gastrointestinal tract at the same sampling time, they were grouped into different branches. Moreover, the species numbers of cladocerans and copepods in paddlefish gastrointestinal tract were more than that in bighead carp's at all sampling times. Meanwhile, the biomasses of food organisms in two fish species gastrointestinal tract were analyzed. The results showed that when cladocerans and copepods were rich in the pond, there was no difference for their biomasses in two fish species gastrointestinal tract (P 0.05); when cladocerans and copepods were lack in the pond, the feeding intensity of paddlefish declined, but the biomasses of cladocerans and copepods was still higher (P 0.05); however, when the cladocerans and copepods disappeared in the pond, the biomass of rotifer in paddlefish increased more (P0.05); in contrast, smaller food organisms were filtered by bighead carp in the different periods. In addition, more bioflocs had been filtered by two fish species as the animal food organisms becoming fewer and fewer. In conclusion, there was feeding competition pressure between paddlefish and bighead carp in the same pond, which was closely related to the larger prey richness in the pond.