| Brachymystax lenok tsinlingensis is a residual species transferring from north to south during the ice age. It belongs to Brcahymystax, Salmonidae, Salmoniformes and is endemic to China. The fish is mainly distributed in the upper reaches and tributaries of Weihe, the tribulary of Yellow River, and in the upper reaches of Xushuihe and Ziwuhe belonging to the tributaries on the north side of Hanshui, the biggest tribulary of Yangtze River. In 1988, B. l. tsinlingensis was listed as the Second Class Protected Animals.However, very few information on the biology and ecology upon the fish has been known,, so that also it is short of basis for protection and management. In this thesis, larvae and juviniles of B. l. tsinlingensis obtained by both artificial and natural propagation was used to experimental materials, and observation on microstructure in otolith of the fish was made. We first reported morphological development, deposition law of growth ring, and a primary estimate on incubation period in natural rivers, and further explored the large-scale marking method by otolith applied to embryo, larvae and juviniles of B. l. tsinlingensis. The main results were listed as follows:1. The newly hatched larvae had two pairs of otoliths, which were sagitta and lapillus, while the asteriscus appeared 24 days after hatching. Otolith shape changed with larval and juvenile development, and the samples from embryonic development of late stage to larval B.l. tsinlingensis's were collected continuously. Three pairs of otoliths were removed from the fish. Morphology of lapillus were undergoing changes from round, ovoid to the undulant margin pear-shape at 55 days. Like the lapillus, the sagitta was round at 1 day after hatching. It then became ovoid and changed into a spindly shape at 7 days.Finally, it became mussel-shape with a long pointed posterior and pointless anterior at 24 days. Compared to the other otoliths, the shape of the asteriscus was relatively stable during growth:it remained fan-like, while it s primordium and core were not as obvious as those in lapillus and sagitta.2. The primordium, nucleus and daily increment on the otoliths could be observed clearly under microscope. The primordium and nucleus were round or oval in shape. Most otoliths had two nucleus and five primordiums. The first growth increment in otoliths was observed on the second day after hatching. The regression analysis showed that there was a linear relationship between the increment number in sagitta and daily age of larvae and juveniles. The regressed equations were: N=0.9805d-0.098 (r2=0.9987,n=77,P<0.001).3. The hatching B. l. tsinlingensis larvae total length was 11.10-11.54 mm. Larvae hatched with a large yolk sac, which was totally reabsorbed by the 18th day, and the growth of larvae in total length (L) can be separated in two stages, which the regressed equations were:L1=0.4589d+10.75 (r2=0.9752,.P<0.001) and L2=0.2688d+14.091 (r=0.9761,P<0.001). Regression analysis showed that there was an exponential relationship between otolith size and fish size until body length of 19 mm or so, and a linear relationship after that size. The regressed equations between the otolith radius (R) and body length (L) were R=5.1254e0.166L(r2=0.9739, P<0.001)in lapillus, and R=3.4805e0.1766L (r2=0.9859, P<0.001) in sagitta when total length was less than 19 mm, and R=-225+17.978L (r2=0.9791,P<0.001) in lapillus, and R=-12.654+6.0604L (r2=0.9255, P<0.001) in sagitta when total length was more than 19 mm.4. The wild B. l. tsinlingensis were collected from Xianyihe,116 individuals of samples were determined randomly the total length of larvae and daily ages of otoliths. Hatched dates were estimated from the daily ages and sampling dates. The daily-age of wild B.l. tsinlingensis ranged from 18 to 41 days, mainly including 26 to 32 days, which accounting for 57.76% of the total abundance. Back-calculated hatching dates of B. l. tsinlingensis in Xianyihe was spread over a long period. Hatching began late-April and continued until late-May, with a prominent peak was in early May, but little was observed after mid-May, indicating that after mid-May only a few eggs were hatched.5. To study the effect of alizarin complexone for marking the B. l. tsinlingensis embryo and larvae, the otolith of larvae were detected by fluorescence microscope. The results showed that the larvae immersed in ALC solution or which from treated embryo presented distinct scarlet-pink fluorescent marks on otolith under UV light. 30mg/L for 18h was found to be the most appropriate for embryo with 100% of marking rate and 91% of hatching and larvae survival rate. The marking effect was " bright mark" .120mg/L for 12h was the most appropriate for the 30 days old larvae with 83.3% marking ratio and 92.3% larvae survival rate after treated for fifteen days, which had no statistically difference with control group (P>0.05). The marking effect was "light mark".Compared with larvae group, embryo group needed lower concentration of ALC and which was more ideal on success ratio of marking, marking effect, post-larvae survival rate and marking cost. This method for marking otoliths of B. l. tsinlingensis with ALC during embryo was recommended and which could be attempted on marking other fish. Furthermore, this could be applied to distinguish hatchery-produced fish from wild fish and which is helpful to assessment of different stock enhancement and surveys of the early life history. |
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