Offshore aquaculture, also known as open water aquaculture or open ocean aquaculture, is an emerging approach to mariculture (seawater aquafarming) where fish farms are positioned in deeper and less sheltered waters some distance away from the coast, where the cultivated fish stocks are exposed to more naturalistic living conditions with stronger ocean currents and more diverse nutrient flow. [2] [3] Existing "offshore" developments fall mainly into the category of exposed areas rather than fully offshore. 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. According to proponents of offshore aquaculture, the wastes from aquafarms that have been moved offshore tend to be swept away and diluted into the open ocean. Moving aquaculture offshore also provides more ecological space where production yields can expand to meet the increasing market demands for fish. Offshore facilities also avoid many of the conflicts with other marine resource users in the more crowded inshore waters, though there can still be user conflicts offshore.
Critics are concerned about issues such as the ongoing consequences of using antibiotics and other drug pollutions, and the possibilities of cultured fish escaping and spreading disease among wild 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. [2] In 2008, aquaculture provided 45.7% of the fish produced globally for human consumption; increasing at a mean rate of 6.6% a year since 1970. [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. [9] In the United States, the future of offshore aquaculture technology within federal waters has become much talked-about. [10] As many commercial operations show, it is now technically possible to culture finfish, shellfish, and seaweeds using offshore aquaculture technology. [10]
Major challenges for the offshore aquaculture industry involve designing and deploying cages that can withstand storms, dealing with the logistics of working many kilometers from land, and finding species that are sufficiently profitable to cover the costs of rearing fish in exposed offshore areas. [11]
To withstand the high energy offshore environment, farms must be built to be more robust than those inshore. [2] [12] However, the design of the offshore technology is developing rapidly, aimed at reducing cost and maintenance. [13]
While the ranching systems currently used for tuna use open net cages at the surface of the sea (as is done also in salmon farming), the offshore technology usually uses submersible cages. [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. [13] They are attached to buoys on the surface which frequently contain a mechanism for feeding and storage for equipment. [13] Similar technology is being used in waters near the Bahamas, China, the Philippines, Portugal, Puerto Rico, and Spain. [13] By submerging cages or shellfish culture systems, wave effects are minimized and interference with boating and shipping is reduced. [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. [13]
Multi-functional use of offshore waters can lead to more sustainable aquaculture "in areas that can be simultaneously used for other activities such as energy production". [14] Operations for finfish and shellfish 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. [16] The institute plans to grow mussels and red abalone on the actual platform, as well as white seabass, striped bass, bluefin tuna, California halibut and California yellowtail in floating cages. [16]
Integrated multi-trophic aquaculture (IMTA), or polyculture, occurs when species which must be fed, such as finfish, are cultured alongside species which can feed on dissolved nutrients, such as seaweeds, or organic wastes, such as suspension feeders and deposit feeders. [17] This sustainable method could solve several problems with offshore aquaculture. [17] The method is being pioneered in Spain, Canada, and elsewhere. [10]
Roaming cages have been envisioned as the "next generation technology" for offshore aquaculture. [13] These are large mobile cages powered by thrusters and able to take advantage of ocean currents. [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. [2] However, implementing such ideas will have regulatory and legal implications. [13]
As oceans industrialise, conflicts are increasing among the users of marine space. [18] This competition for marine space is developing in a context where natural resources can be seen as publicly owned. [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. [22] The problems can be aggravated by the remoteness of many marine areas, and difficulties with monitoring and enforcement. [22] On the other hand, remote sites can be chosen that avoid conflicts with other users, and allow large scale operations with resulting economies of scale. [3] Offshore systems can provide alternatives for countries with few suitable inshore sites, like Spain. [3]
The ecological impacts of offshore aquaculture are somewhat uncertain because it is still largely in the research stage. [2]
Many of the concerns over potential offshore aquaculture impacts are paralleled by similar, well established concerns over inshore aquaculture practices. [23]
One of the concerns with inshore farms is that discarded nutrients and feces can settle on the seafloor and disturb the benthos. [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. [2] However, dissolved and particulate nutrients are still released to the environment. [16] Future offshore farms will probably be much larger than inshore farms today, and will therefore generate more waste. [17] The point at which the capacity of offshore ecosystems to assimilate waste from offshore aquaculture operations will be exceeded is yet to be defined. [17] [25]
As with the inshore aquaculture of carnivorous fish, a large proportion of the feed comes from wild forage fish. Except for a few countries, offshore aquaculture has focused predominantly on high value carnivorous fish. [7] If the industry attempts to expand with this focus then the supply of these wild fish will become ecologically unsustainable. [2]
The expense of offshore systems means it is important to avoid fish escapes. [2] However, it is likely there will be escapes as the offshore industry expands. [2] This could have significant consequences for native species, even if the farmed fish are inside their native range. [2] Submersible cages are fully closed and therefore escapes can only occur through damage to the structure. Offshore cages must withstand the high energy of the environment and attacks by predators such as sharks. [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. [13] However, the fertilised eggs of cod are able to pass through the cage mesh in ocean enclosures. [26]
Compared to inshore aquaculture, disease problems currently appear to be much reduced when farming offshore. For example, parasitic infections that occur in mussels cultured offshore are much smaller than those cultured inshore. [14] However, new species are now being farmed offshore although little is known about their ecology and epidemiology. [2] The implications of transmitting pathogens between such farmed species and wild species "remains a large and unanswered question". [27]
Spreading of pathogens between fish stocks is a major issue in disease control. [27] Static offshore cages may help minimize direct spreading, as there may be greater distances between aquaculture production areas. However, development of roaming cage technology could bring about new issues with disease transfer and spread. The high level of carnivorous aquaculture production results in an increased demand for live aquatic animals for production and breeding purposes such as bait, broodstock and milt. This can result in spread of disease across species barriers. [27]
Aquaculture is encouraged by many governments as a way to generate jobs and income, particularly when wild fisheries have been run down. [2] However, this may not apply to offshore aquaculture. Offshore aquaculture entails high equipment and supply costs, and therefore will be under severe pressure to lower labor costs through automated production technologies. [7] Employment is likely to expand more at processing facilities than grow-out industries as offshore aquaculture develops. [2]
As of 2008, Norway and the United States were making the main investments in the design of offshore cages. [28]
In 2010, the Food and Agriculture Organization (FAO) sub-committee on aquaculture made the following assessments:
The sub-committee recommended the FAO "should work towards clarifying the technical and legal terminology related to offshore aquaculture in order to avoid confusion." [29]
In 2002, the European Commission issued the following policy statement on aquaculture: [30]
By 2008, European offshore systems were operating in Norway, Ireland, Italy, Spain, Greece, Cyprus, Malta, Croatia, Portugal and Libya. [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." [31]
Moving aquaculture offshore into the exclusive economic zone (EEZ) can cause complications with regulations. In the United States, regulatory control of the coastal states generally extends to 3 nm, while federal waters (or EEZ) extend to 200 nm offshore. [10] Therefore, offshore aquaculture can be sited outside the reach of state law but within federal jurisdiction. [2] As of 2010, "all commercial aquaculture facilities have been sited in nearshore waters under state or territorial jurisdiction." [6] However, "unclear regulatory processes" and "technical uncertainties related to working in offshore areas" have hindered progress. [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] In June 2011, the National Sustainable Offshore Aquaculture Act of 2011 was introduced to the House of Representatives "to establish a regulatory system and research program for sustainable offshore aquaculture in the United States exclusive economic zone". [32] [33]
By 2005, offshore aquaculture was present in 25 countries, both as experimental and commercial farms. [7] Market demand means that the most offshore farming efforts are directed towards raising finfish. [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. [2]
The offshore aquaculture of shellfish grown in suspended culture systems, like scallops and mussels, is gaining ground. Suspended culture systems include methods where the shellfish are grown on a tethered rope or suspended from a floating raft in net containers. [14] Mussels in particular can survive the high physical stress levels which occur in the volatile environments that occur in offshore waters. Finfish species must be feed regularly, but shellfish do not, which can reduce costs. [14] The University of New Hampshire in the US has conducted research on the farming of blue mussels submerged in an open ocean environment. [34] They have found that when farmed in less polluted waters offshore, [35] the mussels develop more flesh with lighter shells. [34]
Global status of offshore aquaculture Aquaculture Collaborative Research Support Program [36] | |||
Location | Species | Status | Comment |
---|---|---|---|
Australia | tuna | C | 10,000 tonnes/year worth A$250 million |
California | striped bass, California yellowtail, Pacific halibut, abalone | E/C | Attempts to produce from an oil platform |
Canada | cod, sablefish, mussels, salmon | Mussels established in eastern Canada | |
Canary Islands | seabass, seabream | Two cages installed but not now used | |
China | unknown finfish, scallops | E | Small scale experiments on finfish |
Croatia | tuna | C | 8 offshore cages (1998) |
Cyprus | seabass, seabream | C | 8 offshore cages (1998) |
Faeroe Island | Failed trials | ||
France | seabass, seabream | C | 13 offshore cages (1998) |
Germany | seaweed, mussels | E | Trials using wind-farms |
Greece | seabass, seabream | C | |
Hawaii | amberjack, Pacific threadfin | C | |
Ireland | Atlantic salmon | E | Various experimental projects |
Italy | seabass, seabream, tuna | C | |
Japan | tuna, mussels | C | Commercial tuna ranching, offshore mussel long-lines. |
Korea | scallop | ||
Malta | seabass, seabream, tuna | C | 3 offshore cages (1998) |
Mexico | tuna | E | |
Morocco | tuna | C | |
New Hampshire | Atlantic halibut, cod, haddock, mussels, sea scallops, summer flounder | E/C | Experimental work from the University of New Hampshire, two commercial mussel sites |
New Zealand | mussels | About to become operational | |
Panama | tuna | C | |
Puerto Rico | cobia, snapper | C | |
Spain | seabass, seabream | C | Government assisting trials |
Turkey | seabass, seabream | C | |
Vietnam | barramundi | C | |
Washington | sablefish | C | |
Taiwan | cobia | C | 3,000 tonnes (2001) |
Aquaculture, also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants. Aquaculture involves cultivating freshwater, brackish water, and saltwater populations under controlled or semi-natural and can be contrasted with commercial fishing, which is the harvesting of wild fish. Aquaculture is also a practice used for restoring and rehabilitating marine and freshwater ecosystems. Mariculture, commonly known as marine farming, is aquaculture in seawater habitats and lagoons, as opposed to freshwater aquaculture. Pisciculture is a type of aquaculture that consists of fish farming to obtain fish products as food.
Mariculture, sometimes called marine farming or marine aquaculture, is a branch of aquaculture involving the cultivation of marine organisms for food and other animal products, in seawater. Subsets of it include, fish farms built on littoral waters, or in artificial tanks, ponds or raceways which are filled with seawater. An example of the latter is the farming of plankton and seaweed, shellfish like shrimp or oysters, and marine finfish, in saltwater ponds. Non-food products produced by mariculture include: fish meal, nutrient agar, jewellery, and cosmetics.
Fish farming or pisciculture involves commercial breeding of fish, most often for food, in fish tanks or artificial enclosures such as fish ponds. It is a particular type of aquaculture, which is the controlled cultivation and harvesting of aquatic animals such as fish, crustaceans, molluscs and so on, in natural or pseudo-natural environments. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish hatchery. Worldwide, the most important fish species produced in fish farming are carp, catfish, salmon and tilapia.
Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life or, more commonly, the site where such enterprise takes place. Commercial fisheries include wild fisheries and fish farms, both in freshwater waterbodies and the oceans. About 500 million people worldwide are economically dependent on fisheries. 171 million tonnes of fish were produced in 2016, but overfishing is an increasing problem, causing declines in some populations.
The cobia is a species of carangiform marine fish, the only extant representative of the genus Rachycentron and the family Rachycentridae. Its other common names include black kingfish, black salmon, ling, lemonfish, crabeater, prodigal son, codfish, and black bonito.
A fish hatchery is a place for artificial breeding, hatching, and rearing through the early life stages of animals—finfish and shellfish in particular. Hatcheries produce larval and juvenile fish, shellfish, and crustaceans, primarily to support the aquaculture industry where they are transferred to on-growing systems, such as fish farms, to reach harvest size. Some species that are commonly raised in hatcheries include Pacific oysters, shrimp, Indian prawns, salmon, tilapia and scallops.
Integrated multi-trophic aquaculture (IMTA) is a type of aquaculture where the byproducts, including waste, from one aquatic species are used as inputs for another. Farmers combine fed aquaculture with inorganic extractive and organic extractive aquaculture to create balanced systems for environment remediation (biomitigation), economic stability and social acceptability.
This is a glossary of terms used in fisheries, fisheries management and fisheries science.
As with other countries, the 200 nautical miles (370 km) exclusive economic zone (EEZ) off the coast of the United States gives its fishing industry special fishing rights. It covers 11.4 million square kilometres, which is the second largest zone in the world, exceeding the land area of the United States.
Aquaculture started to take off in New Zealand in the 1980s. It is dominated by mussels, oysters and salmon. In 2007, aquaculture generated about NZ$360 million in sales on an area of 7,700 hectares. $240 million was earned in exports.
Aquaculture in Australia is the country's fastest-growing primary industry, accounting for 34% of the total gross value of production of seafood. 10 species of fish are farmed in Australia, and production is dominated by southern bluefin tuna, Atlantic salmon and barramundi. Mud crabs have also been cultivated in Australia for many years, sometimes leading to over-exploitation. Traditionally, this aquaculture was limited to table oysters and pearls, but since the early 1970s, there has been significant research and commercial development of other forms of aquaculture, including finfish, crustaceans, and molluscs.
The aquaculture of salmonids is the farming and harvesting of salmonid fish under controlled conditions for both commercial and recreational purposes. Salmonids, along with carp and tilapia, are the three most important fish groups in aquaculture. The most commonly commercially farmed salmonid is the Atlantic salmon.
China, with one-fifth of the world's population, accounts for two-thirds of the world's reported aquaculture production.
The fishing industry plays a significant part in the national economy of Pakistan. With a coastline of about 1,120 km, Pakistan has enough fishery resources that remain to be developed. Most of the population of the coastal areas of Sindh and Balochistan depends on fisheries for livelihood. It is also a major source of export earning.
Aquaculture is the farming of fish, shellfish or aquatic plants in either fresh or saltwater, or both. The farmed animals or plants are cared for under a controlled environment to ensure optimum growth, success and profit. When they have reached an appropriate size, they are harvested, processed, and shipped to markets to be sold. Aquaculture is practiced all over the world and is extremely popular in countries such as China, where population is high and fish is a staple part of their everyday diet.
South Korea is a major center of aquaculture production, and the world's third largest producer of farmed algae as of 2020.
Cobia, a warm water fish, is one of the more suitable candidates for offshore aquaculture. Cobia are large pelagic fish, up to 2 metres (6.6 ft) long and 68 kilograms (150 lb) in weight. They are solitary fish except when spawning, found in warm-temperate to tropical waters.
Aquaculture in Madagascar started to take off in the 1980s. The industry includes the cultivation of sea cucumbers, seaweed, fish and shrimp and is being used to stimulate the country's economy, increase the wages of fishermen and women, and improve the regions ocean water quality. Coastal regions of Madagascar are reliant on the Indian Ocean's marine resources as a source of food, income, and cultural identity.
Aquaculture in the United Kingdom is dominated by salmon farming, then by mussel production with trout being the third most important enterprise. Aquaculture in the United Kingdom represents a significant business for the UK, producing over 200,000 tonnes of fish whilst earning over £700 million in 2012 (€793 million).
Fish farming is a major economic contributor to South Australia's seafood sector. The most valuable species is the Southern bluefin tuna, which is caught in the wild then transferred into sea cages in southern Spencer Gulf where they are fed locally caught sardines. The second most valuable species is the Yellowtail kingfish, which is farmed near Port Lincoln and Arno Bay. A tourist venture called Oceanic Victor located in Encounter Bay allows paying customers the opportunity to swim in a sea cage with the Southern bluefin tuna and handfeed the fish. Prominent companies in the fish farming sector in South Australia include Clean Seas and Tony's Tuna International.