Offshore aquaculture
As maritime classification society DNV GL has stated, development and knowledge-building are needed in several fields for the available deeper water opportunities to be realized.
[4] One of the concerns with inshore aquaculture, which operate on more sheltered (and thus calmer) shallow waters, is that the discarded nutrients from unconsumed feeds and feces can accumulate on the farm's seafloor and damage the benthic ecosystem,[5] and sometimes contribute to algal blooms.
Moving aquaculture offshore also provides more ecological space where production yields can expand to meet the increasing market demands for fish.
[3][6] Aquaculture is the most rapidly expanding food industry in the world[7] as a result of declining wild fisheries stocks and profitable business.
[8] In 1970, a National Oceanic and Atmospheric Administration (NOAA) grant brought together a group of oceanographers, engineers and marine biologists to explore whether offshore aquaculture, which was then considered a futuristic activity, was feasible.
[10] As many commercial operations show, it is now technically possible to culture finfish, shellfish, and seaweeds using offshore aquaculture technology.
[2] These large rigid cages – each one able to hold many thousands of fish – are anchored on the sea floor, but can move up and down the water column.
[2][14] Offshore farms can be made more efficient and safer if remote control is used,[15] and technologies such as an 18-tonne buoy that feeds and monitors fish automatically over long periods are being developed.
For example, the Hubb-Sea World Research Institutes’ project to convert a retired oil platform 10 nm off the southern California coast to an experimental offshore aquaculture facility.
[13] One idea is that juvenile tuna, starting out in mobile cages in Mexico, could reach Japan after a few months, matured and ready for the market.
[19] There can be conflict with the tourism industry,[20] recreational fishers,[19] wild harvest fisheries[21] and the siting of marine renewable energy installations.
[5] The "dilution of nutrients" that occurs in deeper water is a strong reason to move coastal aquaculture offshore into the open ocean.
[24] How much nutrient pollution and damage to the seafloor occurs depends on the feed conversion efficiency of the species, the flushing rate and the size of the operation.
[13] The outer netting is made of Spectra – a super-strong polyethylene fibre – wrapped tightly around the frame, leaving no slack for predators to grip.
[3] In Ireland, as part of their National Development Plan, it is envisioned that over the period 2007–2013, technology associated with offshore aquaculture systems will be developed, including: "sensor systems for feeding, biomass and health monitoring, feed control, telemetry and communications [and] cage design, materials, structural testing and modelling.
[6] The five offshore research projects and commercial operations in the US – in New Hampshire, Puerto Rico, Hawaii and California – are all in federal waters.
[10] Two commercial operations in the US, and a third in the Bahamas are using submersible cages to raise high-value carnivorous finfish, such as moi, cobia, and mutton snapper.
[2] Submersible cages are also being used in experimental systems for halibut, haddock, cod, and summer flounder in New Hampshire waters, and for amberjack, red drum, snapper, pompano, and cobia in the Gulf of Mexico.
