Investigations Of Fish Resources In Jiang’an Section In The Upper Reaches Of The Yangtze River

The upper reaches of the Yangtze River is one of the richest areas of freshwater fish species in China.It is estimated that there are 286 species of fish distributed in this section,with as many as 112 endemic species,including 112 species of endemic fish.With the continuous development of water conservancy and hydropower projects in China,many large hydropower stations have been built in the upper reaches of the Yangtze River.The construction of hydropower stations has significantly changed the habitat of this area.The Jiang’an section of the upper reaches of the Yangtze River is located in the buffer zone of the“National Nature Reserve for the Rare and Endemic Fishes in the Upper Reaches of the Yangtze River”.This section is rich in fish resources,including Acipenser dabryanus,Myxocyprinus asiaticus,Procypris rabaudi,Coreius guichenoti,etc.However,there is a lack of research on the fish resources in this section,and the status of fish resources is not clear.In this paper,based on the survey data from 2021-2022,we studied the status of fish resources,the status of early resources and the physical environment characteristics of the Jiang’an section.By evaluating the fish composition and community structure,and analyzed the composition of spawning fish,the status of spawning grounds and abiotic environmental,The aim of this study is to provide basic data for fish resource conservation and the evaluation of the effect of the“10-year fishing ban”.The main research results are as follows:1.From 2021 to 2022,a comprehensive survey was conducted to investigate the fish community in Jiang’an section of the upper Yangtze River.A total of 1,511 fish were captured and identified,representing 45 different species from 9 families in 4 orders.The fish species were mainly Cypriniformes,with a total of 30 species,accounting for 66.67%;Siluriformes followed with 12 species(26.67%);Perciformes with 2(4.44%);Acipenseriformes was the least,only 1 species(2.22%.).Among the Cypriniformes,the Cyprinidae accounted for the most,with 26 species.Followed by Balitoridae,2;Cobitidae,1;Catostomidae,1.During the two-year survey,36 species of fish were collected in 2021and 29 species in 2022,of which 20 species were the same.The similarity index between the two surveys was S=0.62.Among the 45 species of fish,7 were endemic to the upper reaches of the Yangtze River,namely Coreius guichenoti,Gobiobotia boulengeri,Onychostoma angustistomatus,Rhinogobio cylindricus,Rhinogobio ventralis,Leptobotia elongata,Jinshaia sinensis.There were 5 species of aquatic wild animals under the national key protection,namely Coreius guichenoti,Onychostoma angustistomatus,Myxocyprinus asiaticus,Rhinogobio ventralis,Leptobotia elongate.2.Ecological types of catches:Divided by feeding habit,there were 27 species of omnivorous fishes,15 species of carnivorous fishes and 3 species of herbivorous fishes;Divided by habitat layer,there were 24 species of bottom-layer fish,16 species of lower-middle layer fish,and 5 species of upper-middle layer fish;Divided by body size,there were 10 species of large fish,18 species of medium fish and 17 species of small fish;Divided by the type of spawning,there were 22 species of fish spawning demersal eggs,15 species of fish spawning drifting eggs,6 species of fish spawning sticky eggs,and 2species of fish spawning floating eggs.According to the relative importance index IRI,the dominant species in Jiang’an section were Rhinogobio typus and Coreius heterodon.Compaired to 2021,the fishing specification of Rhinogobio typus in 2022 had decreased.The abundance biomass curve(ABC)showed that the fish community in Jiang’an section was moderately disturbed,and the community lost large individual dominant species,mainly small and medium-sized fish.3.Surveys were carried out in Jiang’an section between March-June 2021 and April-May 2022 to study the fish resources of early life.During the 2021 monitoring period,108,932 fish eggs were collected and 17 species were identified,belonging to 3 orders and 6 families.Among them,there were 13 species of Cypriniformes,2 species of Siluriformes and 2 species of Perciformes.In 2022,30,144 fish eggs were collected and20 species were identified,belonging to 3 orders and 7 families.There were 15 species of Cypriniformes,3 species of Siluriformes and 2 species of Perciformes.Through two years survey,at least 27 fish species breed in Jiang’an section,including 12 species of drifting-spawning fish,8 species of demersal-spawning or sticky-spawning fish,and 7endemic fish species in the upper reaches of the Yangtze River.The endemic fish species were Procypris rabaudi,Hemiculterella sauvagei,Xenophysogobio nudicorpa,Sinogastromyzon sichangensis,Jinshaia.abbreviata,Metahomaloptera omeiensis,and Paracobitis potanini.4.During the monitoring period in 2022,4 spawning peaks were observed at sites S1 and S2,while 5 spawning peaks were observed at site S3.It is estimated the total fish eggs passing through the Jiang’an section is 3.94×10~8 ind.According to the diversity index(H’),the diversity of early fish resource was not high,and the evenness index(J)was also relatively low.Environmental factors such as water temperature,p H,dissolved oxygen,transparency,water level and water discharge were found to have different degrees of influence on egg density through redundancy analysis.Among them,dissolved oxygen and p H had significant effects on egg density(P<0.05).The research results showed that the Jiang’an section was a spawning ground for a variety of fish,and the early fish resources were large in scale but poor in diversity.The natural reproduction of Acipenser dabryanus,Myxocyprinus asiaticus was not monitored.Changes in water discharge had a stimulating effect on fish reproduction.The two-year catch survey and early fish resource survey showed that at least 59 species of fish inhabited the Jiang’an section,of which 14 fish species were not surveyed in the catch survey.This suggests that the early fish resource survey plays a supplementary role to the catch survey.5.Acoustic Doppler Current Profiler(ADCP)was used to measure the depth-average-velocity and water depth.The results showed that the depth-averaged-velocity in Jiang’an section ranged from 0.37 to 3.42 m/s,and the average velocity value was2.27±0.48 m/s,with slow flow and rapid flow.The water depth range from 2.57 to 27.49m,and the average depth was 10.61±3.74 m,with shallow water and deep water,which can provide habitats for different fishes.Based on the water flow characteristics,early fish resource survey,and the breeding habits of Rhinogobio typus,it is speculated that Jiang’an section may be a typical spawning area for Rhinogobio typus.