Acta Hydrobiologica Sinica (水生生物学报) 2012/36:6 PP.1081-1086
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 fre-quency and feeding time, so that this fish may utilize diet nutrition more reasonably in the natural feeding rhythm.