Photo credit: Hussein Ali Mohammed Alshihi (Oman) Review: Abdel Rahman El Gamal
Historic information: Artificial reefs have been around for hundreds of years starting in Japan in the 1600s. The sunken or deteriorating ship wrecks and vessels (e.g. cars, bus bodies, and railroad cars) have been utilized to attract fish and enhance fishery in North America and Australia. More developed engineered artificial reef system consisting of concrete cubes have been used in some European countries. There is an ongoing research which seeks and refines materials, design, and placement of artificial reefs.
Rationality and potential benefits: The successful industrial reefs are expected to play the natural coral reefs in providing shelters as well as hard substrate for marine life to colonize and thrive which will evenly lead to enhancing fishery resources as well as the biodiversity. Natural coral reefs may suffer damages caused by variety of sources including increased runoff from the land which leads to deposited silt and sand into the water. The destruction of coral reefs could be also caused by pollution, anchors and fishing nets, and possibly to recreational diving activities.In general, the use of artificial reefs targets to stimulate coral growth and hence to increase fish stocks.
Expected benefits of industrial reefs:
Enhancement of fishery stocks: The process begins with attracting barnacles, then small fish which in turn attract large fish.
Socio-economic benefits to fishermen beneficiaries through enhanced fishery stocks.
Improving the biodiversity status through the homing and come back of particular coral fishes which could been negatively affected due to the damage of natural coral reefs.
Design, specifications and operation of industrial reefs: Most artificial reefs are engineered structures made of synthetics and hardware (concrete, metal, plastic pipes) and placed in the proper sites to enable the reefs to attract encrusting organisms such as corals and sponges to be followed by and then after larger animals. Fisheries research is carried out to refine materials, design, and placement of artificial reefs in specific bodies of water to maximize its efficiencies in attracting sea life. The characteristics of the artificial reefs include its chemistry and surface roughness as a mean to facilitate invertebrate settlement. The use of micro silica during the fabrication of industrial reefs, allows the pH of the concrete mixture to be adjusted to that of sea water which leads to coral growth. The materials used in the artificial reefs should resist rapid corrosion and should not introduce harmful substances into the marine environment. The number, size, design and dimensions of the reefs are critical factors to be considered. When concrete is used in artificial reefs, it should be made of an environmentally-friendly composite which, over time, becomes pH-neutral to encourage coral growth.
Efficiency indicators: In order to evaluate the efficiency of the industrial reefs, proper designed indicators will be required to be included in the design of the reef project. Often, several measurements are recommended including:
Monitoring of coral development: The reefs should be thoroughly examined by divers at regular intervals during the coral development. Cameras, videos and markings are used to evaluate and analyze the outcomes of such survey.
Monitoring of fish population: Monitoring the development and evolution of the fish community may be videoed at regular intervals. Based on the videos images, diversity indices and fish specific abundance is calculated especially when compared with control zones away from the artificial reef. Of particular importance is the survey of juveniles of commercial species as an indicator to the mode of recruitment for commercial fishing purposes.
Monitoring of algae: The collection of algae settlements at regular intervals and the after the analysis could be used to identify settlement patterns of small invertebrates (worms, barnacles and corals).
The two photos show a type of industrial reefs in the Sultanate of Oman
