ABSTRACT

In this study, the experiments of a 1:30-scale model of a flexible, circular net cage with mooring system are conducted in the circulating flume. For geometry and motion measurements, a nonintrusive stereo imaging method is employed, which uses 3 CCD camera systems to take the 2-dimensional photos and then transform them to 3-dimensional visional sketches. Experiment results show a highly mutual dependency between the tension force and the deformation of a flexible net structure. Further investigated are the evolution change of 3-D deformation and the motion of the net cage.

INTRODUCTION

As the world's population increases, so does the demand for seafood, including marine finfish. Landings of marine finfish are beginning to plateau, however, with nearly50% of the major stocks fully exploited (Food and Agriculture Organization of the United Nations, 2000). While the capture fisheries are reaching their full potential, aquaculture continues to expand. Today, marine cage aquaculture is expected to play an increasingly important role in the fish production industry worldwide. Marine aquaculture has been undertaken predominantly in protected near shore waters (Panchang et al., 1997). In Taiwan, as well as in other countries, this has resulted in an increasing number of fish farms installed in near-shore areas. Despite recent activity in cage aquaculture development in Taiwan, significant biological, engineering and socio-issues need to be resolved before cage aquaculture is chosen instead of inland fisheries. A major constraint to marine aquaculture development in Taiwan is suitable water space. Because of environmental and ecosystem issues existing near-shore aquaculture facilities, aquaculture operations need to be moved into more exposed sites. Thus, the feasibility of extending operations into the energetic open ocean has recently been addressed. However, such a transition is not a minor matter, as the suitable species and technologies for this energetic environment are not yet developed to a viable economic scale.

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