长江上游圆口铜鱼的食性分析

FEEDING HABITS OF COREIUS GUICHENOTI (SAUVAGE ET DABRY) IN THE UPPER YANGTZE RIVER

  • 摘要: 2010年春季(4-5月)、夏季(8月)和秋季(10月)在长江上游合江江段采用三层流刺网以3h为间隔昼夜24h连续采集圆口铜鱼样本, 对其食物组成、昼夜摄食节律及季节摄食节律等进行分析和研究。结果显示圆口铜鱼的食谱较广, 其食物种类包括软体动物、甲壳动物、鱼类、水生昆虫、寡毛类和植物碎片等, 其中以淡水壳菜的相对优势度最高, 说明圆口铜鱼是以肉食性为主的杂食性鱼类; 平均饱满指数和平均充塞度的昼夜变化显示其昼夜摄食节律在春季表现为白昼型, 而在夏季和秋季为晨昏型。摄食率随季节变化逐渐降低, 春季摄食率最高, 达93.33%; 秋季摄食率最低, 仅为78.21%; 充塞度和饱满指数均表现出相似的季节变化, 即春季摄食强度明显高于夏季和秋季, 而夏秋两季之间差异不显著。

     

    Abstract: Coreius guichenoti (Sauvage et Dabry) is an important endemic and commercial fish in upper reaches of the Yangtze River. Unfortunately, population size of C. guichenoti decreased sharply in recent years because of overfishing and habitat fragmentation caused by the construction of the Three Gorges Dam and other hydroelectric projects in the middle and lower reaches of Jinshajiang River. Achieving enhancement and releasing is considered to be an important measure to protect this species. In this paper, diet composition, circadian feeding rhythm and season feeding rhythm of C. guichenoti were studied based on specimens collected by drift-net in spring (April-May), summer (August), and autumn (October) of 2010 in Hejiang reach in the Upper Yangtze River. Food items in intestine content of C. guichenoti consisted of mollusks, crustaceans, fishes, aquatic insect, oligochaeta and organic debris, etc. Although there were some differences in diet composition among the seasons, Limnoperna fortunei was no doubt the dominant prey in each season and followed by shrimps and crabs. To analyze the feeding intensity on daily and annual cycles, three different indices were used: feeding rate, fullness and fullness index. The results showed that the circadian feeding rhythm varied among different seasons. The maximum feeding activity in spring occurred in mid-day (12:00), when the fullness reached grade 4. The circadian feeding activity in summer and autumn both exhibited two peaks, one was early in the morning and the other was early in the evening, but night feeding was more active than the morning one in summer whereas the order reversed in autumn. Feeding rhythm also exhibited seasonal variations. Feeding intensity in spring was significantly higher than those in the other two seasons, whereas the difference between summer and autumn was not significant. C. guichenoti showed a great flexibility in its feeding behavior that may be consistent with the daily and annual changes of the food resources in the environment. Furthermore, it seemed that daily feeding activities were seriously affected by daily change of water temperature. The study of feeding habitats of C. guichenoti can provide useful information in conservation and sustainable utilization of fish resource as well as aquaculture, such as feed formulation, meal frequency and feeding time, so that this fish may utilize diet nutrition more reasonably in the natural feeding rhythm.

     

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