The Investigation of the Hydrodynamics of an Artificial Reef

Marine resources have been declining all over the world in recent decades. The natural reefs of the world are experiencing higher use and pressures, resulting in anthropogenic influences that are deteriorating coral reefs and causing poor water quality. Artificial reefs are manmade structures that are placed on the seabed deliberately to mimic some characteristics of a natural reef. (Jensen, 1998). Both Japan and the United States have been using artificial reefs for at least 200 years. The first artificial reef was deployed in Japan in the 1700s, and the primary goal was to increase fish-catch. Nowadays, artificial reefs in Japan involve diversified types, integrated materials, complicated structures and large-scale design. The first documented artificial reef in the United States dates from 1830, when logs and rocks were sunk off the coast of South Carolina to improve fishing (Williams, 2006). In many countries, artificial reefs have become important elements in the plans for integrated fishery management. Diverse shapes for artificial reefs, such as cube reefs, circular reefs, cross-shaped reefs and so on, provide favorable circumstances for fish perching, foraging, breeding and defense from enemies. Most artificial constructions in the marine environment consist of a variety of non-natural materials. At present, concrete is most commonly employed as a reef material, including cubes, blocks and pipes. Concrete has also been used in combination with other reef materials such as steel, quarry rock, tires and plastic (Baine, 2001). Many of the world’s largest artificial reefs have been deployed as part of a national fisheries program in Japan, where large steel and concrete frameworks have been carefully designed to withstand strong ocean currents (Seaman, 2007). Other popular reef building materials include natural stone and rock, the latter constructed from wide-ranging materials including canvas, anchor blocks, and others. The different faunal assemblages associated with artificial reefs are determined by the physical and chemical nature of the reef materials. Walker, et al (2002) quantitatively compared the fish abundance, fish species richness and fish biomass on artificial reef modules constructed of various materials.