Research On Growth And Reproduction Of Gymnocypris Przewalskii

A total of 352 Gymnocypris przewalskii were collected from 6 sampling sites in Qinghai and Qinghai lake Gymnocypris przewalskii rescue center from 2016-8 to 2017-08.We investigated the age,growth and reproduction of the Gymnocypris przewalskii and performed comparative study against data of Gymnocypris przewalskii of different historical periods.We analyzed the characteristics of sex ratio,growth,reproduction and influence factors of different populations of Gymnocypris przewalskii investigated;we also investigated the identification method of differentiating cultured and wild Gymnocypris przewalskii by squama,which provided a theoretical basis and applicable suggestions for resource protection and further development.The main content and conclusions are as follows:1.Confirmation of the age identification material.Among calcic structures of fish,we chose squama and fin ray（we used dorsal fin rays）as age identification material.Reproducibility of identification and age determination of fin ray was high;annual ring as easy to determine and safe to be sampled,which made it a suitable material for Gymnocypris przewalskii.For fin ray,the age marker was only clear in certain areas;due to the large amount of interfering rings or lacking obvious aging markers in some area,it was not suitable for Gymnocypris przewalskii.Besides,it has been shown by other research that using squama to predict the growth of Gymnocypris przewalskii was better than fin ray;the correlation coefficient between age and length was higher and the predicted length was closer to real length with less discrepancy using squama.2.Research about age and growth characteristic.Female Gymnocypris przewalskii population was composed of 3+-11+ age individuals;the male group was composed of 3+-10+ age individuals.Gymnocypris przewalskii caught by grill net account for 52.69% of the total Gymnocypris przewalskii caught in this study.The majority was 4+-6+ individuals with a length of 83-415 mm.The length and weight of both male and female Gymnocypris przewalskii show equal-rate growth.The equations of length and weight growth were:W = 0.000096×2.722（♀）and W=0.000024×2.881（♂）.The growth of male and female Gymnocypris przewalskii was significantly different.The length of female Gymnocypris przewalskii was ignificantly more than male.The growth fitting equation using Fraser-Lee method was:♀:L_i=478.179·(1-e^{-0.089?（t+0.325）}) W_i=1888.498·(1-e^{-0.089?（+0.325）})^2.722♂:L_i=581.335·(1-e^{-0.064?（+0.923）})W_i=2210.669·(1-e^{-0.064?（+0.923）})^2.881The limiting weight of female fish was also higher than male significantly.The difference between theoretical weight and measured weight was not significant;the fish fullness of Bu Ha collecting site was higher than other sites.3.Reproduction characteristic study.The sex ratio of wild Gymnocypris przewalskii population was 1.645:1,among which female individuals were significantly more than male.Besides,the difference of sex ratio might be associated with the selectivity of fishing gear（grill net）.During reproduction period,obvious cutin barb and white pearls showed up on the second branched fin-ray after tail fin of mature male individuals.Therefore,we could determine the sex of Gymnocypris przewalskii based on the morphology of tail fin.In the total reproductive population,the smallest fish was 123 mm long,25.2g weight and the biggest fish was 415 mm long,572.4g weight.Besides,results of this study showed that the average diameter of mature eggs in female fish was 1.939 mm;the length of egg diameter was not significantly correlated to fish length and GSI.The average fecundity was 5384.81 particle,relative average fecundity was 35.09±11.09 particle s/g;average GSI was 10.174%.4.Study about differentiation method of the wild and cultured population.The squama diameter data showed that the squama diameter of cultured individuals was larger than wild individuals with the same age（p<0.05）.With SPSS stepwise critical analysis method,we constructed squama diameter retrieve table in order to predict whether the individual was cultured or wild;the identification accuracy rate was no less than 92.7%.