Feeding Habits And Selectivity Of Schizopygopsis Younghusbandi Younghusbandi Regan

This thesis analyzed the pattern of temporal variation of the species composition, the dominant species, the cells density, the biomass of fish food foundation based on the data from Yarlung Zangbo River near by Xaitongmoin. Feeding morphological characters of 34 S.y.younghusbandi Regan were measured.117 gut contents of one year in order to study the feeding habits and selectivity of the fish, The mainly study results are as follows:1. The investigation of the Schizothorax's food foundation in Yarlung Zangbo River near by Xaitongmoin.①Adherent algae:It includes Bacillariophyta, Cyanophyta, Chlorophta, Xanthophyta, Cryptoohyta, Euglenophyta.②Zoobenthos:It includes adults and larvae of aquatic insects, nematode, macrobiotus, snails and gammarus.③Phytoplankton:It includes Bacillariophyta, Cyanophyta, Chlorophta, Xanthophyta, Cryptoohyta, Euglenophyta, Chrysophyta.④Zooplankton:It includes protozoa, rotifera, nauplii, cladocera, copepods. aquatic organism biomass were low because of low temperature and lack nutrients in Yarlung Zangbo River. Transparency decline, water velocity accelerate, food shortages result of aquatic organism biomass slump when flood period.2. Feeding morphological characters of S.y. younghusbandi Regan:①Cavum oris: Mouth of the fish is inferior position and arc-shaped. The sharply horny sheath of low jaw was used to scrape algae which adhere to stone and sediment.②Gut:The stomchless fish's gut is long. Gut gnarled complex through 3～5 bend enter anus. Those characteristic indicate the fish can have long time to digest algae and hydrophyte③Aill raker:Aill raker is short, small and sparse, those indicate algae and small invertebrates in gut which were come from periphyton④Esophagus and Pharyngeal teeth:Esophagus was thick and short. The peak of pharyngeal teeth is sharp and beaked, the fossette of teeth is wide. Those characteristic indicate the fish could feeding Macroinvertebrates.3. The feeding habits of S.y. younghusbandi Regan:①Diet composition: Periphyton (including Algae, Small invertebrates); Macroinvertebrates including hydropsychidae larvaes, ephydra larvaes, Chironomida larvaes, and hydrophily insect adults; Other food including Gammarus and eggs. Diatoma is the most important food of S.y. younghusbandi Regan②Feeding intensity:S.y. younghusbandi Regan feeding all the year. The highest gut fullness index was in autumn and lowest in winter. The highest Empty gut rate was in summer and lowest in winter. The fish would stop feeding when they breeding.③Seasonal change of diet composition:schoener overlap index and k-w test show that there are no significant differences in each season, developmental stage and sex.④Feeding selectivity:Bacillariophyta and Chironomida larvae of Ivlev's selectivity index near 0,that maybe the fish feeding periphyton while feeding Chironomida larvae at the same time.