Research On Coastal Aquaculture Environmental Carrying Capacity

Marine aquaculture has been practiced for many years and further development is expected in the coming decade in many parts of the world. Marine aquaculture can provide high quality proteins for human beings. With the rapid development of marine aquaculture, many problems appeared, such as environmental pollution, breakout of diseases, etc. Deteriorated environment could result in harmful feedback that may have severe adverse impacts on the marine ecosystem as well as on aquaculture itself. The sustainable aquaculture development will be hampered by environmental pollution. Concerns have been raised about the problem. For the sustainable development of aquaculture, it is an effective management measure to keep the stocking density and pollutant loadings below the environmental carrying capacity. Research on aquaculture environmental carrying capacity have become an urgent problem.From the viewpoint of environmental protection, models have been built in order to determine the aquaculture environmental carrying capacity. Significant results have been achieved as follows:1.Different nutrient loading analysis methods were discussed. In trash fish culturing areas,more waste will be generated because of the lower utilization of feed. A dry matter convertion rate based nutrient loadings analysis method has been developed in this paper instead of traditional food conversion rate. Nitrogen and phosphorus loadings from cage culturing was 308kg/t and 58.7kg/t respectively.The results indicate that it is more critical in trash fish culturing areas. Static release of nutrients from the bottom of the culturing areas has been determined by Fick's First Law. Nitrogen and phosphorus entering the system through molecule diffusion was 0.034mg/m²Â·d and 0.32mg/m²Â·d.2.Factors that will affect the resuspension of sediment were analyzed. Nutrient releases through sediment resuspension was calculated when the bottom shear stress exceeds the critical shear stress for erosion. The nitrogen and phosphorus released from sediment resuspension in Jiaonan Langya Bay offshore cage culturing area were 5.73×10^-4kg/s and 2.09×10^-4kg/s, respectively. It is helpful to systematically analyze the nutrient loadings from cage aquaculture. It is a new idea for the determination of non-point source from marine aquaculture.3.Lagrangian particle tracking model is presented in the present paper. The advantages of particle model is that it can reduce the impacts of grid size.The movement of faecal particles from cage culturing has been simulated by the tracking model. The results show that the impact from particulate organic is around the culturing area, the environmental impact is local but it is accumulative.4.Models for aquaculture environmental carrying capacity were applied in offshore cage culturing of Langya Bay, Jiaonan. The concentration increases of nitrogen and phosphorus are 0.25 mg/l and 0.03mg/l respectively when the culturing area increases upto 3 times of the present scope. The maximum nitrogen discharge amount from cage culture should be less than 2.42t/a, while phosphorus should be less than 0.28 t/a. Otherwise it will exceed the environmental capacity, environmental pollution will appear. The environmental carrying capacity results can provide useful information for the management of aquaculture industry.5.Suggestions and recommendations for sustainable coastal aquaculture development are given. Aquaculture management should be integrated into coastal management. Research on integrated culturing technology, environmental carrying capacity, high quality fish feed development, environmental recoverying technology and so on will help to keep a sustainable aquaculture management.A lot of research on the relationship between aquaculture and the environment is still needed. It is better to be aware of other environmental parameters between the water-sediment interfaces. The development of ecological dynamic models for culturing system will help to provide more accurate message.