Conservation Biology Of Brachymystax Lenok Tsinlingensis

Brachymystax lenok tsinlingensis, of the subfamily Salmonidae, is endemic to parts of the Taibaishan Mountain in the Qinling Mountains, China. The natural population of B. lenok tsinlingensis has declined drastically in recent decades due to damming, mining, overfishing, pollution, and habitat alteration and destruction. It is listed as ’vulnerable’ in the China Red Data Book of Endangered Animals and classified as a second-class state-protected wild animal in China. The need for rehabilitation of B. lenok tsinlingensis has been recognized, and efforts are being made to support its recovery. In this study, we studied the habitat, population, reproductive ecology, genetic diversity and artificial propagation. The main results are as follows:(1) Sixty eight specimens of B. lenok from the Qinling and Amur River were compared, by examining network data with multivariate morphometrics, and conducted comprehensive analysis of the differences between the 2 populations. Our results showed that 16 of 28 measurable data exhibited statistically significant differences; morphological variations between 2 populations were mainly expressed between the snout and anus. It means that there are significant differences between the 2 B. lenok populations. Furthermore, we obtained effective linear discriminant formula to differentiate the 2 B.lenok populations.(2) Population genetic variations and phylogeographical patterns in B. lenok tsinlingensis collected from the Yangtze and Yellow Rivers were investigated based on the 1082-1163 bp control region with partial tRNA and a 912 bp cyt b partial sequence of mtDNA. A high proportion of the genetic variance (96.03%) was distributed among regions, supporting strong geographic structuring of mtDNA polymorphism. Phylogenetic analysis was conducted using Bayesian inference, based on the combined control region and cyt b sequences. Ten haplotypes were assigned to two clades that were associated with geographic region. No haplotype was shared between populations from the Yangtze River and the Yellow River. The mitochondrial results revealed a strong subdivision of genetic structure in populations.(3) From 2009 to 2010, we studied the spawning behavior of B. lenok tsinlingensis in Badu River and Xianyi River with a combination of radio biotelemetry (n=10) and direct observation. We found that:① some adults showed a short distance migration, ② the male and female adults were in pairs, ③ hid in the daytime and came out at morning and evening, ④ had a hiding fixed places. We found five natural spawning grounds of B. lenok tsinlingensis in Qiqiaogou River (a tributary of Xianyi River) by exploratory excavation, and they were all at the outlet of waterfall pools. The natural spawning grounds were all covered by lush vegetation and without direct sunlight. The flow are slow and the substance are mainly sand and gravel. The spawning type of B. lenok tsinlingensis is partial synchronization and 3-7 days were needed in one time spawning.(4) From the year 2009 to 2014, we started the artificial breeding of B. lenok tsinlingensis in Longxian country, Meixian county and Taibai county. By collecting wild adults, artificial spawning, insemination and hatching, we have achieved the success of artificial breeding from the year 2011 to 2014.The brood amount of B. lenok tsinlingensis is 206-2364, the effect time of artificial spawning is 72-117 hours, the accumulated temperature from fertilization to hatching is 195℃.d, and the accumulated temperature from hatching to larvae float is 140℃.d.The SL-W relationship of cultured B. lenok tsinlingensis (15 months old, n=136) is W= 0.0001L2.5589(R2=0.8888) and the mean condition factor is 0.9749±0.1109.(5) The sperm motility of B. lenok tsinlingensis and effects of four environmental factors (Na+, Mg2+, Ca2+, Glucose) were studied. The results showed the sperm life in river water and Balanced Salt Solution(BSS) were 31-40s and 35-58s, the activity ratio of the them were both more than 98%. Under the effection of Na+, Mg2+, Ca2+ and Glucose, the sperm motility of B. lenok tsinlingensis showed a downward trend after the first rise. The best activator concentration of the four factors were 125nmol/L(sperm motion time and sperm life are 23.56s and 38.37s),80nmol/L(sperm motion time and sperm life are 31.81s and 62.81s),40nmol/L (sperm motion time and sperm life are 23.51s and 45.92s), 60nmol/L (sperm motion time and sperm life are 21.68s and 38.84s). The maximum tolerance concentration of the four factors was 200nmol/L,500nmol/L,150nmol/L and 150nmol/L respectively.(6) The effect of three different diets (group 1:pellet feed, group 2:tubificidae, group 3: the mixture of them) on growth of B. lenok tsinlingensis juveniles were studied. Thirty days’research results showed that the body length was significantly affected by the diet, but not for body weight. The mortality of the three groups was 53.33%,5% and 8.33% respectively. Group 3 showed the best growth, higher daily weight gain and instantaneous growth rate with lower mortality. Tubificidae was suitable for the B. lenok tsinlingensis juveniles and pellet feed was suitable in the later stage culture.(7) The effect of four different stocking density (3000/m2,5000/m2,7000/m2 and 10000/m2, N= 4500) on growth of B. lenok tsinlingensis juveniles for 40 days were studied. During the experiment, the juveniles were fed by tubificidae in the earlier and pellet feed in the later period. The death was record each day and growth traits were record every 10 days. The results showed that the survival rate and specific growth rate (SGR) were significantly affected by stocking density, the mortality of the four groups were 5.18%,4.29%,3.56% and 1.66%. The condition factor (CF) was 0.65-0.78 and the mean SGR was 3.01%, the variation coefficients of standard length and body weight were 14.66-18.66% and 58.08-81.59%. The B. lenok tsinlingensis juveniles can be cultured in high stocking density (7500-1000/m2).