Identification Of Larvae And The Status Of Dominant Species Resources In The Xijiang River

Early fish resources are an important part of fish resources supplementation.It is of great significance to study the species composition and occurrence of early fish resources and to protect and rationally develop and utilize fish resources.An important prerequisite for the early research and assessment of fish resources is the accurate identification of larvae species.The sample of this study was from March 1st to October31 st,2018.The early sampling of the drifting larvae was carried out in the early,middle and late days on the Zhaoqing section of the Xijiang River.The morphological method and DNA barcode technology were used to identify the species of larvae,and the early dynamic characteristics and regularity of Gobiidae larvae were studied.The dominant species,Squaliobarbus curriculus,was analyzed for its resources utilization status.The main results are as follows:1.Identification of species of larvae resources.Morphological identification of larvae in 24 species(categories),of which 13 species were identified and 11 categories were identified.They are Salangidae?Pseudolaubuca ?Parabramis and Megalobrama?Culter?Hemiculter?Squaliobarbus curriculus?Labeoninae?Cyprinus carpio and Carassius auratus?Squalidus argentatus?Tilapia smith and Gobiidae.11 species were identified by DNA barcode,and 3 species of larvae were added.They are Ochetobibus elongatus?Mastacembelus armatus and Pterygoplichthys anisitsi.A total of 45 species of larvae were identified,43 species were identified,one species of the genus was identified and the other was not identified.Enriching the types of early fish resources research in the Pearl River.2.The population structure of the early resources of the Xijiang River.There are45 species(categories)of early resources in the Xijiang Zhaoqing section,belonging to6 orders,10 families,and 39 genera.The total number of larvae from May to September is the highest,accounting for 99.58% of the total larvae.It reached the maximum in the whole year in June,accounting for 38.67% of the total number of larvae.From the level of the families,the largest number of Cyprinidea is 94.25%,followed by Gobiidaeis 4.45%,and the proportion of Serranidae?Cobitidae and Cichlidae was 0.53%,0.48%,0.28%.The proportion of each subject is less than 0.10%.From the species level,the number of Squaliobarbus curriculus accounted for 22.86% of the total larvae,followed by Xenocypris davidi/Xenocypris argentea,Pseudolaubuca sinensis,and Pseudolaubuca engraulis,which accounted for 22.11%,16.17%,and 7.91% of the total larvae.3.Time dynamic characteristics of early fish resources.Analysis of the occurrence of larvae showed that from March to April,with the increase of water temperature,a small number of larvae appeared;from May to June,with the arrival of floods,most species to start spawning.The time,frequency and larvae of different kinds of larvae are affected by factors such as water temperature and discharge.4.Early resource research of Gobiidae.The results of DNA barcode identification showed that Gobiidae the composition of the six species of Gobiidae.Species of Gobiidae,Rhinogobius giurinus?Rhinogobius leavelli and Mugilogobius myxodermus account for 93.28%,and the other three types of Yongeichthys caninus,Rhinogobius delicatus,and Rhinogobius cliffordpopei accounted for 6.72%.The results of the study showed that the total fish resources of Gobiidae in 2018 were 7.204 billion,accounting for 4.33% of the total resources.Obtained seasonal supplementation rules of Gobiidae.filling gaps early resource population research.5.Analysis of the current status of Squaliobarbus curriculus.Using the yield per recruitment(YPR)model,the spanning biomass per recruitment(SBR)and the biological reference points method to assess the utilization of Squaliobarbus curriculus in the Zhaoqing section of the Xijiang River from 2009 to 2014.The results show that Squaliobarbus curriculus has an absolute advantage in the early fish resources.The utilization of Squaliobarbus curriculus resources was in the state of growth-type overfishing,which had not caused supplementary overfishing,which was the reason for the continued superiority of the resources of the Squaliobarbus curriculus.However,the ageing of the population indicates that the current fishing intensity and development status of Xijiang has far exceeded the level of sustainable development of the population.Based on the morphological identification and DNA barcode COI gene identification method,the early identification of Xijiang fish resources was carried out,which proved that the COI gene has a good identification effect on early fish resourceidentification,and the early fish resources were also carried out.Research on temporal dynamic characteristics and resource status.In general,this study not only enriches the types of early fish resources research in the Pearl River,but also fills in the identification of larvae species and the early research on resource populations.It also clarifies the species composition,community diversity and population diurnal variation of Xijiang fish early resources.The research on population resources and community structure reveals the basic features of the early resources of Xijiang fish.The research results provide a strong foundation for the scientific study of the follow-up study of the early resources of the Pearl River fish.