| Fish resources are the precious wealth endowed by nature.However,the originally abundant fish resources in our country have been severely destroyed for various reasons in the process of the rapid development of economic and society.Therefore,our country attaches great importance to the protection of fish resources in recent years.Accurate survey methods without damaging fish resources are important means to study and protect fish resources,and have become a hot topic in fish conservation research.It is a new achievement of modern molecular biology to identify fish species by using the genetic material(e DNA)left in the water environment,It has the advantages of not damaging fish,simple operation and high detection efficiency,and has attracted more and more attention.However,the environmental DNA method is still in the development stage,and there are many influencing factors in the application process,which makes the environmental DNA greatly limited in the investigation of fish resources.Therefore,the main factors affecting environmental DNA and its application in the investigation of fish resources were systematically studied in this study,and the following results were obtained:1.e DNA detection results under different temperature conditions showed that the e DNA abundance of the same fish under different temperature conditions had certain changes,The e DNA abundance of Carassius auratus at 18℃ was significantly different from that at 10 and 26℃(P<0.05),the e DNA abundance of Scaphesthes macrolepis at 26℃ was significantly different from that at 10℃(P<0.05),the e DNA abundance of Pelteobagrus fulvidraco at 18℃ was significantly different from that at10℃(P<0.05).2.Comparison of different fish shows that,under the same environmental conditions,the e DNA abundance of Carassius auratus,Scaphesthes macrolepis and Pelteobagrus fulvidraco were significantly different,and was positively correlated with fish biomass(P<0.05).Among the three species of fish,Carassius auratus had the highest e DNA abundance,followed by Scaphesthes macrolepis,and Pelteobagrus fulvidraco had the lowest e DNA abundance.3.By referring to the Fish Records of Qinling Mountains and Fish Records of Shaanxi,combined with relevant research data,a fish e DNA database on Xushuihe River,a branch of Hanjiang River,and Qianhe River,a branch of Weihe River,was constructed based on Cytochrome b genes for accurately identifying the fish species.Among them,the e DNA database on Xushuihe fishes contains 47 kinds of fish in 3 orders and 6 families,while the Qianhe fishes e DNA database contains 32 kinds of fish in 3 orders and 5 families.According to the e DNA data analysis,cytochrome b gene is effective for classification and identification of most fishes.But it takes Hemibarbus maculatus and Hemibarbus labeo,the Rhodeus ocellatus and Rhodeus sinensis is identical with the cytochrome b gene sequence is used to identify,new primers or other gene fragments need to be screened for further identification.4.Comparative analysis results of different investigation and identification methods show that,generally,the identification results of e DNA fish based on the freshwater fish database of Shanghai Personal Biotechnology Co.,LTD have great deviation,can not meet the needs of natural water fish inventory survey,However by constructing e DNA database of relevant river fish,errors in identification can be effectively eliminated.Although the number of fish species identified was significantly higher than that of traditional survey methods,it was not possible to identify fish with a smaller biomass.Therefore,it cannot accurately reflect the true composition of fish.From the actual results,the e DNA fish survey and identification method optimized in this study is only consistent with the identification results of traditional fish survey methods within a large investigation range,but the results of local investigation and identification vary greatly.In conclusion,although e DNA of fish is positively correlated with biomass of the same species,under the same environmental conditions,e DNA abundance of different fish was significantly different.Therefore,e DNA can only be used for identification of fish species,but can not be used for relative quantitative analysis among different fish,and the e DNA fish survey method needs to be further improved. |
