Offshore Aquaculture: Development, building and testing of a deep water mooring system
Emphasis on healthy and safe foods has boosted seafood consumption. At the same time, increased demands for the sustainable use of seafood have encouraged farming and cultivation instead of fishing for wild species. Limited space in coastal areas, however, is hampering global aquaculture production. It is therefore expected that aquaculture and the cultivation of seafood will increasingly move out of the shelter of bays and fjords and more into open sea areas. This change will increase the demands on equipment for offshore fishing, as work will need to be done at greater depths and to deal with conflicts caused by offshore waves and ocean currents. Concrete blocks and traction anchors are traditional equipment for aquaculture production of seafood, but aquaculture manufacturers are now looking for safer and cheaper methods of attaching their equipment to the seabed. Concrete blocks and tug anchors are unsuitable as anchors as they are expensive and need to be very heavy to be used on the high seas, as well as they require a lot of space as they do not withstand vertical conflicts from the environment and / or service boats. Large ships with powerful equipment must be used to bring them far from shore, and this is a very costly operation. Tæknistál ehf. has developed an underwater drill based on new technology that attaches a light screw anchor to the seabed, all the way down to a depth of 70 meters, without the assistance of divers. The project was carried out in collaboration with Matís ohf., Siglfirðing ehf., Ocean Rainforest spf., Offshore Shellfish Inc., SINTEF MRB (R&D) and partly financed with a grant from Tækniþróunarsjóður and NORA. The drill is light, weighing about 900 kg, and is based on a three-point frame with three screw drills at each corner that attaches it to the seabed. Then a screw anchor, up to four meters long, is drilled into the seabed with a fixed service line. Due to the light weight of the bearing, it is possible to use traditional service boats for fire / cultivation, to anchor. Compared to traditional anchors, such as concrete blocks and tow anchors, such drill anchors are considered more environmentally friendly, cheaper and can withstand much more vertical effort and therefore require much less space for fire / cultivation. Such properties are important for aquaculture / cultivation in the sea, but no less for other uses such as floating docks or ammunition. The drilling rig that was developed in the project has passed various effort tests, but it was also tested in mussel farming under real conditions for the open sea for 6 months in Eyjafjörður. Tests took place during the winter in the worst conditions and showed that the anchors held perfectly and withstood the load much better than traditional anchors (concrete blocks) did at the same time. Marketing of products and technical solutions developed in the project is well under way.
With ever increasing seafood consumption and greater environmental concerns for healthier and safer products, the demands on aquaculture production are rising. Limited space for suitable aquaculture sites along coastal zones is now recognized worldwide as a serious limitation for this important industry. The farming or cultivation of seafood is therefore expected to shift increasingly from sheltered fjords and bays to more exposed offshore culture sites. This expansion offshore, away from the visibility of coastal communities, means installing and anchoring aquaculture infrastructures at greater water depths in rough sea. Thus, in order to eliminate the logistical difficulties imposed by transporting and positioning heavy deadweight concrete anchors or drag ‐ anchors offshore, aquaculture operators are seeking more cost ‐ effective and practical mooring solutions like deep water drills using light ‐ weight anchoring systems. Compared to traditional fish farming in sheltered fjords and bays, offshore aquaculture gear requires a much greater holding power as it is highly exposed to considerable physical forces eg by waves and currents. One of the remaining challenges for this offshore expansion is the costly installation of heavy concrete or drag ‐ anchors to hold the aquaculture infrastructures at considerable water depths. Producers are therefore looking for more cost ‐ effective and reliable mooring systems that can be quickly and easily installed, to meet the increased biomass potential. Taeknistal Inc. has developed a new technology to fasten light ‐ weight helical screw anchors into the seabed, at water depths up to 70 meters below surface, without the assistance of divers. The project was carried out in collaboration with Matis Inc., Siglfirdingur Inc., Ocean Rainforest spf., Offshore Shellfish Inc., SINTEF MRB (R&D) and partly financed by grants received from the Technology Development Fund in Iceland and NORA. An innovative drill machine was specially developed for installing helical screw anchors into the seabed. The submersible structure consists of a triangular drill frame with three small drills, using helical screws that are fixed to each corner of the triangle at the bottom of the drill unit. This drilling machine has the advantage of being light ‐ weight, approximately 900 kg, and can be managed by an ordinary aquaculture service vessel. Compared to the traditional anchor types, such as concrete blocks or drag ‐ anchor, the helical screw anchors are more environmentally friendly, less expensive and more resistant to vertical tension. These are all important factors in aquaculture, especially offshore where one can expect high waves and strong currents, in addition to the tension imposed by the larger service vessels when they are attached to the aquaculture lines. Managing the innovative drill machine was tested at open sea and the holding power of the anchors was tested in actual conditions during six winter months, where the screw anchors were drilled into the seabed at an offshore aquaculture site at Eyjafjordur (North Iceland). The results from this test demonstrated that the screw anchors have a holding capacity superior to that of traditional anchors which minimizes the loss of crop, and reduces the environmental impact. Marketing of the products and the technical solutions developed in the project is well under way.
