The Study On The Morphology Of Feeding Organs And The Feeding Habits Of Six Schizothoracine Fishes

All the six Schizothoracinae fishes(Ptychobarbus dipogon,Oxygymnocvpris stewarti, Schizopygopsis Younghusbandi,Schizothorax o 'connori,Schizothorax macropogon and Schizothorax waltoni) have an importantly economic value,however,the resource is limited,some species are trasuralbe.Along with the ecnomic development of Tibet region,the need for the aquatic products becomes larger,there exsits over-fishing trend in some areas,therefore,it is necessary to further study and analyze for the sustainable utilization of Tibet fish resourece.167 individuals of six Schizothoracinae fishes were collected in Rikeze reach of Brahmaputra Rive from May to July.Comparative morphological structure of the digestive tract in six Schizothoracinae fishes were observed in this study,measured and calculated the correlative data.The food species of six Schizothoracinae fishes and feeding competition among them were studied.The main results are as follows:1.The morphological structure of digestive tract of Six Schizothoracinae fishes The digestive tract includes oral cavity,pharynx,esophagus and intestine.①The magnitude of the horny sheath of lower jaw and the mouth cleft in six Schizothoracinae fishes are different,Oxygymnocypris stewarti＞Schizopygopsis Younghusbandi＞Schizothorax o'connor＞Schizothorax macropogon＞Schizothorax waltoni＞Ptychobarbus dipogon.And the position of mouth of six fishes except Oxygymnocypris stewarti is inferior②There are not jaw teeth,oral cavity teeth,and mobile lingua in these fish species. The special variations in pharyngea bone and pharyngeal teeth were observed.Most of pharyngea bones show arc in shape.Except that the pharyngeals of Schizothorax o 'connori presents oblique-truncate,the pharyngeal teeth in other fishes are tip.③There is a distinct dividing line between the esophagus and the intestine.All of the mucosal folds of esophagus show vertical-drape.Except for Oxygymnocypris stewartii, the ratios of gut length to body length of the other five fishes are all beyond 1 The mucosal folds of intestine are displayed in Z shape in six fishes.2.Feeding habit and Feeding competition of six Schizothoracinae fishes①Schizothorax o'connori and Schizopygopsis Younghusbandimainly feed on periphytic algae.Oxygymnocypris stewartii mainly feeds on small fishes.While,aqutic insects and benthic invertebrates are the primary diets of Schizothorax macropogon, Ptychobarbus dipogon,and Schizothorax waltoni.Six fishes display the feeding preference to a certian extent.②The dietary overlap coefficient and food diversity indices among them was caculatcd using weight percentage of each food species.The results suggested that the degree in feeding competition among the four pairs was very high.It was observed that six fishes might reduce the degree in feeding competition through feeding partitioning. There are greatly differences in the extent of food utilization among six Schizothoracinae fishes.③Periphytic algae and benthic invertebrate are main food of six fishes.The abundance of food is the most key biological factor to determine the population amount, which has great significance in supervising the fishery resources.④The morphological structures in the alimentary canal of six Schizothoracinae fishes have adapted well to the feeding types and feeding habits.The adapted characteristics primarily exhibit whether the horny sheath exists and developes,the morphological structure of pharyngeal teeth,the length of intestine,and so on.