| The Jialing River is the largest tributary of the upper reaches of the Yangtze River Valley with area of 16 square kilometers. Jialing River system composed mainly by the mainstream of Jialing River, Fujiang River and Qujiang River, the complex basin(the different riverbed and hydrologic environment ect.) which provides survival environment for fish. With environment pressures of the cascade hydropower development and unreasonable fishing, sewage, soil erosion and so on,the fishery resources of Jialing River is under great threat in spite of which is plentiful.Pengan which was at the northeast of Sichuan belongs to the shallow hilly areas, and with two hydropower station as well as Jin Xi power plant and Ma Hui power plant, is the miniature of the cascade development of the Jialing River. The establishment of the hydropower station has enriched the resources of water and electricity, which has created enormous benefits for Pengan country. At the same time, it also made the living environment of the fish is damaged, and resulting a large number of poor adaptability of the population to reduce, such as Myxocyprinus asiaticus,Onychostoma sima, Procypris rabaudi and so on. Therefore, this article selected the Pengan section of the middle reaches in the Jialing River as the research object,analysed the strcture of fish communities composition, dynamic change and biology research of the important economically fish, to explore the impact of changes in the water environment on fish community, and provide a theoretical basis for the use and protection of fish resources of Jialing River.The results of this study are as follows:1. Analysis of field data collected by the Pengan section of the middle reaches of Jialing River fish: The total fish collection of 57 species, belonging to 3 orders, 10 families and 40 genera, Cypriniformes most accounted for 75.4% of the total number of species of fish, Siluriformes accounted for 19.30% of the total fish species,Perciformes at least, accounted for 5.26% of the total fish species. Cypriniformes mainly with Gobioninae of Cyprinidae in fish, a total of 22 species accounted for19.30% of the total species. In addition, we based on the fish fauna division standard,the investigated fish can be divided into East Asian Group(50.88%) and the Later Tertiary Period Primitive Group(49.12%).2. Division of ecological types of fish: from the angle of feeding habits, the proportion of aquatic insect feeding fish is high(21.05%), and the proportion of aquatic plant feeding habits and feeding habits of fish is the lowest(5.26%); from thewater fish habitat, the fish(31 species), accounting for 54.39% of the total number of fishes; from the perspective of thermophily, the eurythermic fish accounted for54.39% and the fish are suitable at 5℃~25℃ accounted for 46.61%.3. By the relative importance index(IRI), the dominant species composition of fish community was analyzed. Advantage on the middle reaches of Jialing River Peng’an segment is Hemiculter leucisculus, Saurogobio dabryi, Xenocypris davidi,Pseudolaubuca sinensis, Cyprinus carpio, Carassius auratus, they accounted for catch 62.78% of material weight, and accounted for 67.88% of the total catches.4. The diversity analysis showed that Pielou uniformity index(J’) little fluctuation; Margalef richness index(D) in October 2014 appeared the maximum value(5.46), 2014 August was the lowest(3.27) and generally higher in autumn;Shannon-winner diversity index(H’) is volatility. Summer and autumn is relatively high, and appears maximum(3.59) in January 2014, minimum(2.16) in January 2015.5. Analysis of species diversity and seasonal dynamics of main fishes: there are11 main species in spring, 9 in summer, 14 in autumn and 10 in winter. In hierarchical clustering analysis and divided into two taxa as well as autumn/winter and summer/autumn, and significant difference(R=0.482<1, P<0.05); species hierarchical clustering analysis and divided into two groups: Hemiculter leucisculus,Pseudolaubuca sinensis, Xenocypris davidi, crucian carp, Saurogobio dabryi and Siniperca chuatsi, Mystus macropterus, Cyprinus carpio, Erythroculter ilishaeformis,Erythroculter mongolicus, among groups was significantly(R=0.796<1, P<0.05).6. The population structure analysis on several major economic fish, all samples were divided into 5 age groups. The 2-year-old of Crucian carp, Hemiculter leucisculus, Saurogobio dabryi were dominant and males were excess female individuals, and Xenocypris davidi in one year old fish dominant, the proportion of 5age fish in each population was less. T-test showed: different gender of Crucian carp,Hemiculter leucisculus and Saurogobio dabryi showed no significant difference.Body length and body weight showed significant differences between male and female of Xenocypris davidi.7. In this study, Crucian carp and Xenocypris davidi were uniform growth,indicating that nutrition conditions to meet the growing need of fish on the middle reaches of Jialing River Pengan; Saurogobio dabryi and Hemiculter leucisculus were non uniform growth. The fatness of Crucian carp in 2 ~ 4, Hemiculter leucisculus fertilizer full around 1, and these two kind of fish showed females slightly larger thanmales in addition to age 1 fish; Xenocypris davidi except in one year old fish, the remaining age showed for male than female; Saurogobio dabryi is no big difference in each of the age of the female and the male, fatness compared near. |
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