| Gymnocypris przewalskii,which has a long life cycle,It has the characteristics of slow growth,long life cycle and lake river migration in biology.It is affected by factors such as intensified climate change,overfishing in early years and frequent human activities,from 300000 tons in the 1950 s to the lowest2,743 tons in the 1990 s,the conservation work was not paid attention until the end of the last century.However,The Gymnocypris przewalskii still faces serious threats from hydraulic engineering,crop irrigation,and the drying up of rivers.Therefore,it is particularly important to protect the existing natural spawning grounds and maintain natural reproduction for the restoration of Gymnocypris przewalskii resources,How to enlarge the scale of natural reproduction and improve the efficiency of reproduction has become an urgent task.In this study,we built a simulated spawning environment,studied the behavioral preferences of Gymnocypris przewalskii in different simulated environments,and managed to induce natural reproduction of wild migratory populations in simulated environments through environmental regulation,to understand their breeding behavior and environmental needs,to clarify their ecological needs for natural breeding,and finally to provide technical support for screening and optimizing the environmental conditions of Gymnocypris przewalskii reproduction and rebuilding the natural spawning grounds in Qinghai Lake.The main findings are as follows:1.According to the in-situ investigation results of natural spawning sites in the field,this study was carried out in a controlled environment to artificially simulate naked carp in Gymnocypris przewalskii,and Reproductive migration population of Gymnocypris przewalskii in the breeding season of 2019-2021,and successfully induced the natural reproduction of wild migratory parents.The artificial simulated spawning environment is more stable than the natural environment,and at the same time,the environmental factors can be precisely regulated,According to the reproductive behavior and reproductive effect of parent fish,the induced reproductive rate in artificial ecological environment increased from 27.5% to 67.8% after 3 years,and through continuous improvement and optimization of environmental parameters,the reproductive effect can be significantly improved,a preliminary understanding of the Gymnocypris przewalskii artificial spawning environment construction technology.2.Based on the experiments of indoor riverbed texture preference,artificial simulated spawning site construction and field natural spawning site modification,and combined with the techniques of marker tracking and Ethovision XT behavior tracking,the authors studied the riverbed texture preference of Gymnocypris przewalskii,the law and effect of natural reproduction induced by pebble bed were systematically studied.The results showed that there were significant differences in habitat selectivity of Gymnocypris przewalskii,sand and gravel with sand,and the Gymnocypris przewalskii preferred to stay in the sandy bottom before and after birth(p < 0.05),however,natural reproduction occurs only in pebbles,and although the breeding period is longer in the sand bed,the Gymnocypris przewalskii into the pebble bed is very high.So during the breeding season,the Gymnocypris przewalskii prefer the pebble bed.By comparing the reproductive effects of the blank group,the fine sand group,the silt group and the pebble adding group,the results clearly show that the Gymnocypris przewalskii in the blank group and the silt group will not naturally lay eggs,but the pebble group,as well as the blank and muddy sand formations,natural reproduction was induced immediately after the addition of pebbles,indicating that the natural reproduction of Gymnocypris przewalskii depended on the pebble bed.In order to verify the results,this study artificially laid the whole pebble bed in the field spawning ground.The behavior and spawning monitoring showed that the pebble bed could induce the sediment selection preference of the Gymnocypris przewalskii,according to the above research results,it can be seen that eggs and pebbles can increase the number of eggs,it is suggested that pebble bed is a necessary condition for inducing natural reproduction of Gymnocypris przewalskii.3.In addition to the requirement of sediment,using the method of single factor test,the most suitable environmental parameters for natural reproduction of wild migratory population in artificial spawning environment,such as velocity,temperature,water depth,light and so on,were selected.Precise regulation of water depth and flow and monitoring of breeding induction are carried out by means of gradient increasing.The results showed that the parents could reproduce naturally at the depth of 10-45 cm,the flow rate from still water to 0.8 m/s,and the best propagation effect was obtained at the depth of 20 cm and the flow rate of0.3-0.4 m/s,the results showed that natural reproduction could be successfully induced by Gymnocypris przewalskii under the conditions of total darkness and daylight rhythm,and the reproduction effect of long dark and short daylight rhythm was the best At the same time,the instantaneous water temperature of 35 mating behaviors in field spawning grounds and artificial spawning grounds were monitored by temperature recorder.The statistical results showed that the average instantaneous water temperature of Gymnocypris przewalskii was 13.82℃.This study not only optimizes the construction technology of artificial spawning environment,but also fills the data gap of Gymnocypris przewalskii ’ s reproductive microhabitat requirement,which provides the theoretical basis for further behavioral ecology research.4.In order to elucidate the reproductive behavior pattern of Gymnocypris przewalskii,this study defined typical behaviors including chasing,accompanying,diving,splashing,mating,and so on,by means of marker tracking and video monitoring.The act of splashing,in which the dorsal fin of a single female or male emerges and smacks the surface with the tail,is observed for the first time and is often mistaken for mating.The average reproductive frequency of chasing,accompanying,diving tail and splashing was 5.7 times per day,14.7 times per day,9.3 times per day and 3.5 times per day,respectively.The results showed that of the 34 observed mating behaviors,32(94.1%)were mated by one female and one male.The study also found that the sexually mature female Gymnocypris przewalskii is a one-time oviposit type,with multiple mating and ovulation in a short time.Female and male mating behavior(ovulating and fertilizing)is about3-9 times a day,and each ovulation takes about 4-9 seconds,the average number of ovulation was 131(range 15-376),and each female could lay eggs continuously for 3-7 days.Of the 34 observed mating behaviors 31(91.1%).It occurred at night(23:00-2:00 the next day),and 3(8.9%)occurred during the day(6:00-7:00 in the morning).This is the first systematic observation to define the reproductive behavior of Gymnocypris przewalskii based on artificial spawning conditions.In this study,experimental simulation and artificial regulation were used to achieve spontaneous mating and oviposition of Gymnocypris przewalskii in artificial environment,and precise regulation and measurement of experimental biology and artificial environment were used,the study reveals the Gymnocypris przewalskii’s habitat and reproductive preferences and ecological needs for the substrate,and for the first time systematically defines the characteristics of the Gymnocypris przewalskii ’ s reproductive behavior,establishes and improve the construction technology of artificial spawning ground.This will provide theoretical basis and technical support for future decision-making of habitat protection and resource protection of Gymnocypris przewalskii. |
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