Development And Application Of Rigid-flexible Netting Cage With Copper Alloy Expanded Net

Because of anti-fouling, efficient, healthy and environmentally friendly properties, copper alloys chain link netting has been widely applied in fisheries engineering fields especially aquaculture equipment such as net cage, and good results have been obtained. In the coastal waters of China, a large quantity of copper alloy chain link nettings have being used. Based on their corrosion-resistant and antibacterial activities, the copper alloy chain link nettings provide a good water exchanges inside and outside of cages, keep water a stable dissolved oxygen, ensure the growth rate of the fish and the value of fish products, reduces infection mortality of fish and relieves pressure on water quality near the farm. However,due to its structural defects,the mesh intersection always been in the state of wear and tear, causing its working life not long. On the other hand, widely used gravity cages have a poor adaptability for current, their volume will loss seriously in bad weather. This paper introduces an innovative frustoconical rigid-flexible copper alloy expanded netting cage which both has a long-term use and can maintain a good rate of volume.Frustum shape is designed, upper circumference is 40 meters and bottom circumference is 32 meters. Since the weight of copper alloy expanded nettings itself, the whole netting bears certain tension that can offsets part of flow resistance. As a result, the cage achieves the purpose of maintaining a high volume ratio. In order to install the cage quickly and conveniently offshore, it was combined with rigid modules and flexible modules, and then the rope is penetrated into the collar of modules.In the model cages test, large scale is 6.7, small scale is 2.5 and 3.Testing and observing resistance values and deformation of cages at different water velocities, as well as compare results with polyethylene model cage. It was found that relation of cage whose small scale is 2.5 between water velocities and resistance values can best reflect the actual situation in seawater. Test also showed copper alloy expanded netting cages have significantly better performance to keep volume than polyethylene netting cages.During the cage cultured large yellow croaker, researcher collected regularly its underwater video and tested the breaking force values of each module component after 1, 2 years, those breaking force values were still relatively high, indicating to meet the culture requirements. The results also showed that weight loss rate of copper alloy expanded netting is relatively low, it can be used for a long time. By comparing the production, survival and growth rates and other economic indicators, found that actual economic and cost-effective of copper alloy expanded netting cage cultured large yellow croaker were better than polyethylene netting cage cultured large yellow croaker.It can be expected, under the circumstances of the market demand, industry trends and policy support, copper alloy expanded netting cages will play an indispensable role in the sustainable development of aquaculture, and its prospects will be immeasurable.