| Xiajiang Hydro-junction is located in the valley of upper reach at Baqiu Town,Xiajiang County,in the middle reaches of Ganjiang River,it is the fourth cascade project of the Ganjiang River Basin.It is a large-scale water conservancy project integrating flood control,power generation,navigation and irrigation.The Xiajiang A transverse clapboard fishway for fish reproduction was built in Xiajiang hydro-junction for feeding and winter migration.For evacuate the fishway fish effect,in September 2019 to August 2020,the fish community structure above and below the dam and in the fishway in the Xiajiang Section of Ganjiang River was investigated quarterly,and laboratory test were carried out on the objects and specifications of fish in the catch.It provided parameters for the design and improvement of the fishway velocity of the Xiajiang Hydro-junction,and also To provide technical support for the protection of fishery resources in Ganjiang River.The main results are as follows:1.A total of 79 species of fish were sorted in the Xiajiang Section of Ganjiang River,belonging to 6 orders,19 families and 56 genera,among which 56 species of Cypriniformes belonging to 5 families,accounted for 70.88%of the total species.55species of fish was collected from above the dam and 75 species below the dam.The dominant species were Squalidus argentatus,Ctenopharyngodon idella,Aristichthys nobilis,Hemiculter leucisculus,Hypophthalmichthys molitrix,Squaliobarbus curriculus and Cyprinus carpio.Among them,the populations of Squalidus argentatus,Hemiculter leucisculus,Zacco platypus,Xenocypris argentea and Squaliobarbus curriculus accounted for 30.22%,11.47%,6.10%,5.47%and 4.7%,respectively.Ctenopharyngodon idella,Aristichthys nobilis,Hypophthalmichthys molitrix,Cyprinus carpio,Squaliobarbus curriculus and Megalobrama amblycephala accounted for 27.69%,22.53%,9.85%,8.75%and 6.30%of the total weight,respectively.The four major Chinese carps accounted for large weight percentage,and the main components are Ctenopharyngodon idellus,Aristichthys nobilis and Hypophthalmichthys molitrix.They are also the main targets for the fish passage of the Xiajiang Water Hydro-junction.2.A total of 42 species of 4605 individuals were captured in the fishway of Xiajiang Hydro-junction,belonging to 4 orders,9 families and 34 genera.There are23 species of settled fishes,accounting for 54.76%of the total number of species,the most omnivorous fish were 24 species,accounting for 57.14%of the total numbers of species,17 species of bottom fishes were the most,accounting for40.48%of the total species,18 species of drifting eggs were the most,accounting for 42.86%of the total numbers species.Compared with other domestic fishways,there are more species of fish passing through the fishway of the Xiajiang Hydro-junction.3.The the fishway of Xiajiang Hydro-junction is mainly composed of small and medium-sized fish,The range of body length is 2.3cm?48.5cm,the range of body weight is 1.1-2053.7g,and most body length less than 30cm.The top five by quality of individuals was Zacco platypus,Squalidus argentatus,Hemiculter leucisculus,Saurogobio dabryi,Culter alburnus,were 17.24%,14.42%,11.38%,6.91%and 5.86%resepctively,and The top five by weight was Ctenopharyngodon idella,Cyprinus carpio,Culter alburnus,Squaliobarbus curriculus,Parabramis pekinensis(39.85%,10.39%,9.98%,8.32%and 6.55%,respectively).Among the migratory fishes of rivers to lakes,161 grass carp(3.5%),206 Squaliobarbus curriculus(4.47%),60 Pseudobrama simoni(1.30%),3 Anguilla japonica(0.07%)was collected,and Aristichthys nobilis,Hypophthalmichthys molitrix and Mylopharyngodon piceus of the four major Chinese carps were not found in the fishway.The number of individuals of passing fish varies seasonally,and the number of passing fish is highest in summer,accounting for 42.23%of the total,while the number is least in winter,accounting for 11.69%of the total.Factors affecting the results of fish passing are mainly related to water temperature and water level.4.In this study,we take four major Chinese carps as research objects.We measured the critical swimming speeds of the four major Chinese carps under five temperature gradients(10?,15?,20?,25?,30?).The results showed that the relative critical swimming speeds of Mylopharyngodon piceus,Ctenopharyngodon idellus,Hypophthalmichthys molitrix and Aristichthys nobilis were(3.93±0.24?9.94±1.65)BL·s-1,(3.50±0.48?10.55±2.07)BL·s-1,(0.95±0.04?4.68±0.58)BL·s-1and(2.22±0.18?3.95±0.23)BL·s-1,respectively,across 10??30?.The absolute critical swimming speed and relative critical swimming speed of the four major Chinese carps increased with the increase of water temperature during 10?-20?.The absolute critical swimming speed and relative critical swimming speed reach the maximum at 20?,and then tend to be more stabilization.The swimming capability in the 20?was significantly higher than those in 15?and 10?,but no significant difference with those in 25?and30?.In addition,the critical swimming speeds of C.idellus increased faster than the other three species of the four major Chinese carps as the temperature increases.Under the same temperature,the critical swimming speeds of C.idellusp and M.piceus are similar,and significantly higher than those of H.molitrix and A.nobilis(P<0.01).According to the results of this study,we suggested that the opening time of the fishway should be extended in summer of the year,and the critical swimming speed of Aristichthys nobilis should be taken as the main basis of fishway design. |
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