Community Structure of Fishery Resources and Biological Study of Main Economic Species in Dianshan Lake
|School||Shanghai Ocean University,|
|Keywords||Dianshan Fishery resources Population structure Biological research|
Dianshan is located at the junction of the three regions of Shanghai, Jiangsu, Zhejiang, latitude 3l ° 04'-3L ° 12 '; east longitude 120 ° 53'-121 ° 01', is the largest freshwater lake in the outskirts of Shanghai. The Dianshan both runoff regulation, agricultural irrigation, shipping traffic, aquaculture, landscape, leisure, water sports and other functions, plays an important role in the life and economic development of Shanghai Municipal People's. In recent years, the Dianshan aquatic species gradually decreased to reflect the water quality indicator species or even disappear, traditional fish resources were also damaged, the Dianshan Lake ecosystem population structure has undergone great changes. For the Dianshan ecosystem deterioration from 1985 to 2005, the fence culture measures, but has been shown to cause a decline in water quality. Since 2005, Shanghai began to invest a lot of funds for the Dianshan the proliferation of releasing fish, releasing species silver carp and bighead carp, its function is mainly located in the fishermen income and ecological restoration, has already shown good results for the improve the income of fishermen, and promote water ecosystem restoration and protection of the Lake District fishery resources have played a positive role. Dianshan, however, there is still a lot of problems, such as resources decline, overfishing, declining water quality. In view of this, the idea of ??\, major economic species biology, catch rates were systematically studied, in order to provide a scientific basis for the sustainable use of fishery resources in Dianshan Next Dianshan Lake proliferation of releasing more orderly, more effective carried out. The results show that: June 2010 - March 2011 Dianshan 10 gill nets and 10 shrimp trawl survey, a total of 41 fish samples collected in the survey, belonging to 9 orders, 18 families, 35 genus. Cypriniformes fish dominant, a total of 3 families, 21 genera and 26 species, accounting for 47.82% of the number of species. Relative abundance the Dianshan dominant species knife brachygnathus, the spot bar interpretive and sub o comb goby, accounting for 32.52% of the total number of individuals in the sample, 20.26% and 16.45%. Compared with the history of several investigations, fewer species. Sun Jingyu, Dai Xiaojie survey with 2006, the species has increased, but more serious phenomenon of small fish. Lead to smaller fish of the important reasons is cool over-fishing and fisheries, many fish of the economy, including the sharp drop in breeding colonies of large predatory fish, small fish stocks surge; addition and the proliferation of releasing. March 2011 and July 2010, the diversity index higher, while lower in January 2011; evenness index and dominance index variation is not very obvious. Beginning in June, the overall diversity index showed a slow downward trend in January to a minimum, and then upward trend. Seasonal differences are obvious. The Dianshan site diversity index difference is not obvious. Strong selectivity of gill nets, mesh size greater impact on catches. By comparison, the greater the gill net mesh size, type and quantity of captured catch less; diversity index and richness index showed a decreasing trend with increasing mesh, it means that the mesh The smaller, the more severe the damage on the Dianshan fish resources. The economic species silver carp and bighead carp occurred mainly in the 8cm and 10cm gill nets, mesh, 4cm and 6cm mesh rare. If you want better protection Dianshan fish stocks, it is necessary to strictly control the mesh size of gill nets. Dianshan silver carp and bighead carp slower growth rate compared with other waters. Proliferation of releasing excessive, shrimp trawling, silver carp and bighead carp living environment change is the major cause of the the Dianshan Lake silver carp and bighead carp growth slower. Carp, bighead carp mainly to blue-green algae for food, the Dianshan silver carp and bighead carp in summer relative fatness higher, silver carp and bighead carp releasing the proliferation of cyanobacteria bloom outbreak of the suppression function. Economic species silver carp and crucian carp catch rates are slowly decreasing trend as the month changes, seasonal changes are more obvious, have a relationship with the fishing season. Carp and bighead carp catch rates have been relatively low, the month did not change significantly. In order to better management and utilization of the Dianshan fishery resources, the need to adjust the structure of fishing operations, strengthening closed seasons, closed areas and fishing gear and methods management, the implementation of the harvest specifications and mesh size restrictions and carry out industrial restructuring fisheries resources management measures to achieve the Dianshan sustainable fisheries development purposes.