| The Qinghai-Tibet Plateau is known as the"third pole of the earth"and an important ecological and safety barrier for China.Schizothoracids is one of the dominant groups of Tibetan fish.During March to May and September to November in 2019,a total of 249S.thermalis,185 P.kaznakovi and 215 S.nukiangensis,the only three Schizothoracinae fishes in Tibet section of Nujiang River,were collected from 8 locations.The adaptability of their annual growth and morphological differentiation were analyzed,and the main results are as follows:1.The otoliths of three fishes were used as age identification materials to compare their the age and growth characteristics were.The results showed that 16 age groups were identified（2-17 years old）in the S.thermalis samples,among which the proportion of 4-year-old group was the highest at 17.5%,and the second was 3-year-old,accounting for15.2%.the oldest was 17 year,accounting for only 0.9%with 2 individuals.There are 17age groups（2-17,23 years old）of P.kaznakovi,among which the proportion of 4-year-old group was the highest at 24.9%,and the second is 6-year-old,accounting for 15.1%.the 17-year-old and 23-year-old are the lowest,accounting for only 0.5%.There are 15age groups（2-16 years of age）in S.nukiangensis,the proportion of 3-year-old group was the highest at 22.5%,and the second is 2-year-old individuals,accounting for 16.2%.and the proportion of 16-year-old fish is at least 0.5%.The strong relationships between body length and weight were tested for the three species with S.thermalis of W=2×10-5L2.8833（R2=0.9915,n=249）,P.kaznakovi of W=1×10-5L 2.9524（R2=0.9942,n=185）and S.nukiangensis of W=2×10-5L 2.9259（R2=0.9948,n=215）,which indicated that S.thermalis belonged to be an allometric growth type.The Von Bertalanffy,Logistic GF and DCF functions were used to fit the growth curve of S.thermalis,and the result showed that the Von Bertalanffy equation can better.The Von Bertalanffy equation was also used fitted the growth curves of P.kaznakovi and S.nukiangensis,for the two fish being constant growth.Von Bertalanffy growth functions of the 3 species were described as S.thermalis of Lt=409.3[1-e-0.099（t-0.89）]and Wt=889.1[1-e-0.099（t-0.89）]2.8833,P.kaznakovi of Lt=505.3[1-e-0.089（t-0.14）]and Wt=1415.5[1-e-0.089（t-0.14）]2.9524 and S.nukiangensis of Lt=538.5[1-e-0.096（t-0.53）]and Wt=2007.1[1-e-0.096（t-0.53）]2.9259.The inflection point age of the S.thermalis is 11.56 with the body length of 226.5mm and the weight of257.9 g,deducting from the function.The inflection point age of the P.kaznakovi is 12.35 with the body length of336.5mm and the weight of 426.6 g,and that of S.nukiangensis is 11.56 with the body length of 354.4mm and the weight is 589.9 g.The S.thermalis have relatively small limit body length,inflection point age,and inflection point body length-weight,whereas those of S.nukiangensis was the largest among the three species.2.The 37 morphological characteristic parameters of the samples were measured to explore the intraspecific and interspecific morphological differentiation The PCA showed that the cumulative contribution rate of the top five principal components was 81.1%.S.nukiangensis appeared relatively short snout length,relatively long dorsal fin base length and relatively caudal peduncle wide.The results showed that there was significant differentiation between three species,Among which,S.nukiangensis has the shortest kiss length,the highest tail handle wide and the longest tail handle length,whereas most of the morphological characteristic value of P.kaznakovi were the largest and the smallest for S.thermalis.As intraspecific analsis,morphological differentiation between Babu population and the others of S.thermalis was obvious.Chavalon polulation S.nukiangensis also expressed divergence from the other populations.Four morphological characteristic parameters of Basu population of S.thermalis were less than those of Loron,Bianba,Biru and Nagqu populations and other four parameters were greater.The four morphological features of S.nukiangensis Chavalon population are less than the other,while other 5 morphological features are greater.Relative large kiss length may help fish to fix in rapid water. |
