| Schizothorax prenanti belongs to genus Schizothorax, subfamily Schizothoracinae, Family Cyprinidae order Cypriniformes. Schizothorax prenanti is a unique species cold water fish in China. Schizothorax prenanti mainly distributed in the Yangtze River, Jinsha River, Minjiang River, Dadu River, Qingyi River and Xi River. The main producing areas are in Ya’an, Sichuan. In this experiment, about 673 Schizothorax prenanti samples were collected in the lower reaches of the Jinsha River on 2012-2013. Biological characteristics and population ecology of Schizothorax prenanti were studied. The main results show that:1 The body length of the samples are in the range of 49-395mm to 101-220mm, the dominant (percentage number 75.04%); the body weight of they are in the range of 2.1-926.8g, mainly in the range of 2.1-160g (percentage number 83.36%), Optimum formulation between body length and body weight can be expressed:W=2* 10-5L2.9678, R2=0.9829. The growth formula is based on body length and body weight, the von Bertalanfy formula equation of Schizothorax prenanti is Lt=624.1 (1-e-0.151 (t+0.8281), Wt=3951.71 (1):e-0.151 (t+0.8281)) 2.9678. The inflexion point for the growth were 6.38 years old, the inflection age body length is Li=413.81mm, Wi= 1167.26 g body weight. After 6.38 years old, the acceleration of weight is less than 0, the population growth come into the decline stages.2. Schizothorax prenanti fed on the algae (mainly to the Navicula, the Nitzschia and the Cymbella), the zooplankton (mainly to the amoebae), the aquatic insects (mainly to the chironomid larvae), fish (mainly to the Hemiculter leucisculus), mud, and plant detritus. The most important food for Schizothorax prenanti is the algae and the aquatic insects, and the amoebae.3 The reproductive period fish were studied. The results show that:Schizothorax prenanti’s breeding season was during late November to early May next year in the lower reach of the Jinsha River; The female and male ratio was 1.67:1. Mature coefficient (GMC) of the average value is 0.64%, variation range of 0.02-10.01%. At first maturity Schizothorax prenanti’s Standard length and age were 267.05mm and 2.87years. All the fishs’fertilized eggs were measured, the average diameter of mature egg size is 0.21cm, the fluctuation range is 0.14-0.27cm. The average value of absolute fecundity was 2604 eggs/fish, the fluctuation range is 893 to 5416 eggs/ fish, the average relative fecundity was 12 grains/g, ranged from 6 to 22/g. Embryo development in ovary were not synchronized, there were different egg size in one ovary. Schizothorax prenanti would spawn many times during a year.4. Schizothorax prenanti’s total mortality coefficient was 1.42 per year, natural mortality was 0.3276 per year and fishing mortality coefficient was 1.09 per year. The development rate was 0.77 per year. According to the spawning stock biomass per recruit model, we could come to a conclusion that the fish resources of Schizothorax prenanti had been over developed.5. A total of 13 variable loci were detected in the 1154bp sequence of the mtDNA D-loop in the population.25 haplotypes were identified from 59 individuals according to the determined sequence. The average haplotype diversity was 0.906, nucleotide diversity was 0.291. Genetic differentiation can be seen between Schizothorax prenanti in Qiaojia section of the Jinsha River and that of Sui River section of the Jinsha River.6. By using SSR, the genetic diversity of Schizothorax prenanti in Qiaojia section and that of Sui River section was analyzed. Suijiang group received a total of 80 alleles per locus, and 8 alleles, the average expected heterozygosity was 0.6836. Jinhe group received a total of 75 alleles per locus, and 7.5 alleles, the average expected heterozygosity was 0.6367; there were no significant genetic differentiation between Qiaojia Schizothorax prenanti group and Jinhe group. |
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