张氏的食性分析

ANALYSIS ON THE FEEDING HABITS OF HEMICULTER TCHANGI

为分析长江上游干支流梯级水利开发对张氏(Hemiculter tchangi Fang)的生态效应,在已对该鱼繁殖生物学、年龄与生长和形态性状进行研究的基础上,对张氏食性进行分析。针对采自四川省合江县的张氏样本,探究其食物组成;并分别比较不同季节、不同年龄组别、性腺不同发育期的样本的摄食状况。结果显示:张氏是偏动物性食性的杂食性鱼类。摄食双翅目昆虫(蚊蝇幼虫)、草本植物及种子、藻类、环节动物门寡毛纲(水蚯蚓)、膜翅目昆虫、甲壳类、枝角类、鞘翅目昆虫、贝类以及小鱼、鱼卵、幼蛙等。动物性饵料在夏季出现次数百分比最高,冬季最低;而藻类在冬季出现百分比高于其他季节。平均充塞度和摄食率均以春季为最高,秋季最低。在1—4龄鱼中,摄食率随着年龄的增加而增大。对于雌鱼而言,处于Ⅱ期的鱼类个体肠道内食物平均充塞度高于其他各期;而对于雄鱼,处于不同性腺发育期的样本,平均充塞度和摄食率则无规律性变动。在其繁殖季节5—9月期间,未出现停止摄食的现象,平均充塞度和摄食率处于中等水平。

Hemiculter tchangi Fang is an endemic fish in the upper Yangtze River,and mainly distribute in Sichuan Province and Chongqing City.At present,more and more researches have used endemic fish as indicative species to appraise the healthy of the river which they lived.Further more,the habitat changed dramatically due to the construction of a series of hydroelectricity projects,it was forecasted that the population sizes of the endemic fish might decreased sharply in the future.It is very urgent to make suitable countermeasures for the conservation and resource-recovery of those endemic species.This paper preliminarily analyzed the diet composition and its variation over seasons,years and different developmental phases of gonad.72 specimens were collected from the estuary of the Chishui River,the first-order tributary of the Yangtze River,which locating at Hejiang county of Sichuan Province.The contents of the alimentary tracts of H.tchangi were analyzed to establish diet composition.The results indicated that H.tchangi was omnivore-fish stressing on animality.The diet compositions of H.tchangi included dipterans（i.e.larval mosquito and fly）,plants and their seed,algae,oligochaeta（i.e.freshwater earthworm）,hymenopterans,crustacean,cladocera,cole-opteran,mollusks,small fish,fish eggs,larva frog and so on.Dipterans,plants and their seed,algae were the most im-portant groups according to occurrence ratio.Variation in food composition among sampling sites was high.This high variation appears to be primarily associated with differences in prey availability,but much less with prey size selectivity.Feeding intensity varied considerably among seasons.The occurrence frequency of animal bait reached to its highest in summer,whereas the peak of algae was in winter.The highest food fillness and feeding rate appeared in spring when energy-rich food was needed for the final maturation of gonads,while the lowest appeared in autumn.This was mainly because that the metabolism and motility of fish was much higher than other seasons when the water temperature and the richness of food were in the highest status.The feeding rate increased with age growing from 1 to 4.This phe-nomenon suggested that the predation capability grew with age and body-length growing.But the food fillness did not take on such regular changing pattern.The relationship between food fillness,feeding rate and different developmental phases of gonad of this fish were as follows： the food fillness was much higher in Ⅱ phrase than other gonad develop-mental phases to the female,while there was no such phenomenon to the male.This was mainly because that the female need much energy to propagate.The fish feed in the propagated period too.But the food fillness and feeding rate were both in the medium state in the reproductive stage.The phenomenon that H.tchangi is an omnivore preying on terres-trial insects was emphasized.It was hypothesized that the outer of terrestrial insects were covered with chitin shell,so they can not be easily digested in a particular time span,often leaved compounded eyes,appendage and so on.These materials are obvious indicators that can be easily found and observed under the microscope.To be contrast,the species which lived in freshwater,like freshwater earthworm and larval mosquito,have no such strong protection all over the body,so they were digested more easily by predators without any body parts left.After the construction of several dams,the former flowing water became stable and slow.This may affect the feeding habit and the living situation of H.tchangi.