Studies On Age And Growth Of Schizothorax O'connori In Lhasa River In Tibet

125 individuals of Schizothorax o'connori were collected from Tibetan Lhasa river during August 15^th to September 5^th, 2003. Based on observation of annuli on otolith, anal scale, vertebra and opercular, the age and growth of S. o'connori were studied. The results were summarized as follows:1. The features and checks on anal scale, otolith, vertebra and opercular were described. On the anal scales, there were annuli as well as false ring, first check and spawning check. With significant variation in shape and other features of the anal scale, the annuli on the anal scale were ridged. And there were Crichton effect on the rear edge of anal scale. The annuli on otolith was more obvious, but there were still some false ring and periodic discontinuities on some of the otolith. About 29% of specimen couldn't be aged. The annuli on vertebra was obvious except unappraisable initial check and edge check. The growth rings on the opercular were turbulent and the annuli were unappraisable. Over 70% of specimen could not be age-determined with opercular.2. The main age groups with otolith appraisal range from age-S to age-9, accunting for 88.1% of total specimen. The main age groups with anal scale, vertebra and opercular all ranged from age-4 to age-8, which account for 88.2%, 86.3% and 92.7% respectively in anal scale, vertebra and opercular. The age appraised with otolith is one year elder than that appraised with other three materials.3. Comparison of annuli among four materials, otolith is the best material for age determination in S. o'connori while the opercular is the poorest. The supplementary material for age determination in S. o'connori is vertebra.4. Analysis of the growth of otolith showed that otolith growth was related to body growth with linear relationship under the same age, but was no significant with age under the same body length.5. The relationship of body length and body weight was W - 0.0213L^2.828. von Bertalanffy growth formula for body length was L_t =55.4×(1.-e^[-0.0943(t+0.8749)]) and thatfor body weight was W_t =1816×(1-e^[-0.0943(t+0.8749)])^2.828.6. There were two inflexion age on the growth acceleration curve of body weight, one was between age-2 to age-3, which was peculiar for highland fish; Inflexion age on the growth rate curve of body weight was age-10.1, which was neither the age of the first sexual mature, nor the age of aging inflection.7. According to the comparison of back-calculated value, theoretical value and measured value, we found that back-calculated value was closely to measured value, It was indicated that the growth of appraisal was closely with the growth of fish body; von Bertalanffy equation could describe the growth course of S. o'connori, but it could not express the growth course of S. o 'connori completely.8. According to the various results above the text, we drew a conclusion that the spawning age of 5. o'connori was about age-5.