Characteristics of Community Structure and Influencing Factors of Fish Larvae and Juveniles in the Backwater Area of Typical Tributaries of the Three Gorges Reservoir
To explore the temporal and spatial variations in the community structure of fish larval and juveniles and its relationship with environmental factors in the backwater area of tributaries of the Three Gorges Reservoir(TGR),a survey of fish larval and juvenile resources and habitat status was performed in the backwater areas of 6 tributaries(Longxi River,Wujiang River,Xiaojiang River,Modao River,Daning River,and Xiangxi River)from March to June in 2019 and 2020.Based on the survey data,the study was conducted to examine the spatiotemporal variations in species composition,relative abundance,and community structures of fish larval and juveniles in different months,different tributaries and different sampling nets.The cor-responding relationship between community structures and environmental factors was also analyzed.The results showed that a total of 43 species of fish larvae and juveniles were collected,including one endemic species in the upper reaches of the Yangtze River,and two exotic species.In terms of species richness,Xiaojiang River had the highest number of species(29),while Daning River had the lowest(11).11 fish species,including Rhinogobius giurinus,Pseudolaubuca engraulisare,and Neosalanx taihuensis,were dominant ones(accounting for 98.85％of the total).Principal component analysis revealed the significant monthly variations in the community structure of fish larvae and juveniles.The peak time of occurrence for fish larvae and juveniles is earliest for herbivorous fish such as Cyprinus carpio and Carassius auratus,followed by small fishes that feed planktivores,such as Hyporhamphus intermedius,Hemiculter bleekeri,Rhinogobius giurinus,Rhodeus ocellatus,and Neosalanx taihuensis,and finally by carnivorous fishes with medium or large size,such as Siniperca chuatsi.The community structure of fish larvae and juveniles also exhibited obvious differences among different sampling rivers.Compared to the other rivers,there were more larvae and juveniles of C.carpio and C.auratus collected in Modao River and Xiaojiang River.Canonical corresponding analysis based on integrated hierarchical partitioning indicated that the river of the sampling site,dissolved oxygen content,water temperature,substrate type,and pH value were the most important environmental factors influencing the variation in the community structures of fish larval and juveniles.The results of random forest model showed that the dissolved oxygen content,water temperature,water level,and the river of the sampling site were the key factors affecting the density variations of larval fishes and juveniles.It was recommended to strengthen the protection of the fish larvae and juveniles in the backwater area of TGR tributaries through water level regulation and control of exotic species.
the Three Gorges Reservoirfish larvae and juvenilescommunity structurebiotic-abiotic relationshiprandom forest model
NETL
NSTL
万方数据
