| Mystus nunerus belongs to Siluriformes, Bagridae, Mystus. It lives in the r ivers and lakes of southeast Asia, it is one china's economic freshwater fishes. It is also distributed in down-stream area of Lancang River. A total of 145 specimens of Mystus nunerus were collected from down-stream area of Lanca ng River during the period from 2009 to 2010. According to the samples det ermination, the paper studies the characteristic of Mystus nunerus and its pop ulation dynamics, main results are as follows:1.Based on the analysis of Mystus nunerus exhibited catch, Mystus nunerus r epresented 73.1% of the total catch in Dinong. July, August, September surve y of catch in both its appear. Mystus nunerus is in the average weight of cat ch for 9.32%. July, August, September is at or near to 14%, and it have a lo w proportion in January and April, one-year-old individual have 30; 2-year-old individual have 20; 3 years of individual have 30; 4 years old individual ha ve 37. Range of length is 5.3cm to 74.6cm, the minimum length is 5.3cm, th e maximum length was 74.6cm, with corresponding weights of 4.2g and 4500 g respectively.2. The result identified by vertebra is larger than the result identified by o toliths. Two results in higher relative in younger individuals, handling and ide ntification of Otolith was more complicated. vertebra was easyer to handling. Just soaked, and then put them apart, it is more convenient to operate andsuit able for large-scale identification of age.3. The relationship between body length and weight. female W=0.0104L3020; male W=0.0105L3.17; Von Bertalanffy equation: female Lt=76.43(1-e-0.23(t+1.91)); Wt=4312.21(1-e-0.23(t+1.91))3.20; male Lt=74.11(1-e-0.24(t+1.82)); Wt=4156.87(1-e-0.24(t+1.82))3.174. Sex and Sexual maturity of fish was identified based on the body shap e and the shape of reproductive opening. The mature female fish abdominal s lightly swollen and soft; Male fish had a 2.0cm reproductive axon.5.The spawn type of Mystus nunerus is the tail repeat spawning type. So me 2 years old individuals of Mystus nunerus reach sexual maturity at 3 year sold fully reach sexual maturity, fulling degrees is on the rise in April to Jul y, full degrees fell rapidly after August.6. Mystus nunerus eat a variety of foods. Check it's gastrointestinal tract. The diet was dominated by shrimp, fish, shellfish, also include mosquito larv ae of wave, screw, organic clastic, aquatic insects, diatoms, organic clastic, gr een algae, cladoceras classes.7.The total mortality calculated from the length converted catch curve was 0.59 year-1 for female and 0.6 year-1 for male Mystus nunerus. Natural morta lity was 0.22 year-1 for female and 0.24 year-1 for male, And fishing mortalit y was 0.59 year-1 for female and 0.6 year-1 for male, assessing the stock stat us using the B-H model, we concluded that the resource of Mystus nunerus h ad already been overfished.To protect this resource,the fishing mortality coeffic ient must be reduced, and the first capture age should be put off by limiting the mesh. |
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