| Poyang Lake,the largest freshwater lake-wetland of China,provides abundant fishery resources.Carp and crucian carp is the dominant population of the Poyang Lake fish.Their eggs adhere to the hydrophyte for further incubation.The catch yield of carp and crucian carp made up nearly a half of the Poyang Lake's whole catch yield.Supervising the change of spawning site of carp and crucian carp will be of great importance in the protection of fishery resources.In this research,we use water depth data getting from the four years sampling to build the digital elevation model(DEM)of the Benghu Lake and Dachuchi Lake lakebed.Then,we use the Landsat 8 satellite images to extract the water extent of the two lakes from March to August in 2014.Combined with the DEM result and the suitable spawning condition(water depth and vegetation),we screened and masked the water extent images to get the potential spawning site for the carp and crucian carp.At last,we compare our potential spawning site with the result of resources investigation carried out by Jiangxi Fisheries Research Institute in 2014.The results show that,from March to August,with water levels rose the water extent has grown,and the location and range of potential spawning site we calculated changed.We suggest,considering that the location and range of potential spawning site will change following the change of water level,we can take more specifically protective measures.In addition,for the reason of we only take water depth and vegetation into consideration to screen the spawning site,the result range and location may be optimized if we take the water temperature,vegetation type and flow field as controlling factors to forecast the spawning site.The results of this study include the following aspects:(1)Dahuchi Lake in the wet season and the Poyang Lake main lake into a piece,the water level changes.But in the dry season when the Poyang Lake water level decreased when a certain height,Dahuchi lake and Poyang Lake Lake area was completely isolated from the natural dike,the formation of closed water wetlands.Therefore,in the dry season,regardless of how the Poyang Lake Lake water level changes,the lake water level has always maintained a certain level of volatility.So Dahuchi lakeide Lake Beach outside the water line is more intensive,informative,and the lake area is no water line can be extracted.Therefore,the waterfront line extraction method is used to construct the Poyang Lake bottom elevation model,and the detailed terrain information of the lake area can not be obtained.The field water depth data can be obtained in the lake area of water depth,to make up for the water line extraction method defects,to solve this problem.Through the Dahuchi lake water extraction results can be seen that every summer typhoon season,the rapid rise in the lake,to 7-8 months of the lake rose to the highest value,after the water level began to fall.(2)Lake grass around the lake,will be flooded by seasonal water;lake edge of the shallow part of the water can receive sunlight for photosynthesis,suitable for submerged plants,water plant growth.Both of these environments have become suitable places for carp to lay eggs.In March 2014,the forecast area of the carp spawning ground in Dahuchi lake was 1438200m2,the area of the grasses outside the spawning ground was 3954600m2,and the total area of the aquatic plants in the lake was 5392800m2.In May 2014,And the total area of the aquatic plants outside the spawning ground is 5,989,500m2,and the total area of the aquatic plants in the lake is 7,924,500m2.In June 2014,the spawning ground of the carp in Dahuchi lake Lake is forecast to be 1,071,900m2,For 14,149,800 m2,the total area of lake water plants is 15,221,700 m2.According to the Jiangxi Provincial Institute of Fisheries Science in 2014,the area of the spawning ground of the carp and crucian carp in Dahu Lake reached 17,390,000m2,which was much larger than that of the experiment.This may be due to the limited range of water depth is too small,and the field investigation can not be very precise,often some non-spawning grounds are counted as spawning grounds,so the field survey spawning area is often more than the spawning ground The situation is bigger.May fixed water depth spawning area is greater than March,and May than the March water level change is small,spawning area changes from aquatic plants germination,aquatic area increased.June fixed water depth spawning area is less than 5 months is because the water level changes,the selected fixed water depth regional location from the flat lake area to the slope of the larger lake,so the water depth of the same,smaller area The Therefore,the growth of aquatic plants and water level changes in the spawning field play a role. |
PDF Full Text Request