From Wikipedia, the free encyclopedia
Aquaculture production by region
Aquaculture (less commonly spelled aquiculture), 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 (e.g. lotus). Aquaculture involves cultivating freshwater and saltwater populations under controlled or semi-natural conditions, and can be contrasted with commercial fishing, which is the harvesting of wild fish. Mariculture, commonly known as marine farming, refers specifically to aquaculture practiced in seawater habitats, opposed to in freshwater aquaculture.
Aquaculture can be conducted in completely artificial facilities built on land (onshore aquaculture), as in the case of fish tank, ponds or raceways, where the living conditions rely on human control; on well-sheltered shallow waters nearshore of a body of water (inshore aquaculture), where the cultivated species are subjected to a relatively more naturalistic environments; or on fenced/enclosed sections of open water away from the shore (offshore aquaculture), where the species are exposed to more diverse natural conditions such as ocean currents, diel vertical migration and nutrient cycles.
According to the Food and Agriculture Organization (FAO),
aquaculture "is understood to mean the farming of aquatic organisms
including fish, molluscs, crustaceans and aquatic plants. Farming
implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc. Farming also implies individual or corporate ownership of the stock being cultivated." The reported
output from global aquaculture operations in 2014 supplied over one
half of the fish and shellfish that is directly consumed by humans; however, there are issues about the reliability of the reported figures. Further, in current aquaculture practice, products from several pounds of wild fish are used to produce one pound of a piscivorous fish like salmon.
Particular kinds of aquaculture include fish farming, shrimp farming, oyster farming, mariculture, algaculture (such as seaweed farming), and the cultivation of ornamental fish. Particular methods include aquaponics and integrated multi-trophic aquaculture, both of which integrate fish farming and aquatic plant farming. The Food and Agriculture Organization describes aquaculture as one of the industries most directly affected by climate change and its impacts. Some forms of aquaculture have negative impacts on the environment, such as through nutrient pollution or disease transfer to wild populations.
Overview
Global capture fisheries and aquaculture production reported by FAO, 1990-2030
World aquaculture production of food fish and aquatic plants, 1990–2016.
Harvest stagnation in wild fisheries and overexploitation
of popular marine species, combined with a growing demand for
high-quality protein, encouraged aquaculturists to domesticate other
marine species.
At the outset of modern aquaculture, many were optimistic that a "Blue
Revolution" could take place in aquaculture, just as the Green Revolution of the 20th century had revolutionized agriculture.
Although land animals had long been domesticated, most seafood species
were still caught from the wild. Concerned about the impact of growing
demand for seafood on the world's oceans, prominent ocean explorer Jacques Cousteau
wrote in 1973: "With earth's burgeoning human populations to feed, we
must turn to the sea with new understanding and new technology."
About 430 (97%) of the species cultured as of 2007 were
domesticated during the 20th and 21st centuries, of which an estimated
106 came in the decade to 2007. Given the long-term importance of
agriculture, to date, only 0.08% of known land plant species and
0.0002% of known land animal species have been domesticated, compared
with 0.17% of known marine plant species and 0.13% of known marine
animal species. Domestication typically involves about a decade of
scientific research.
Domesticating aquatic species involves fewer risks to humans than do
land animals, which took a large toll in human lives. Most major human
diseases originated in domesticated animals, including diseases such as smallpox and diphtheria, that like most infectious diseases, move to humans from animals. No human pathogens of comparable virulence have yet emerged from marine species.
Biological control methods to manage parasites are already being
used, such as cleaner fish (e.g. lumpsuckers and wrasse) to control sea
lice populations in salmon farming. Models are being used to help with spatial planning and siting of fish farms in order to minimize impact.
Aquaculture production (2019)
The decline in wild fish stocks has increased the demand for farmed fish.
However, finding alternative sources of protein and oil for fish feed
is necessary so the aquaculture industry can grow sustainably;
otherwise, it represents a great risk for the over-exploitation of
forage fish.
Another recent issue following the banning in 2008 of organotins
by the International Maritime Organization is the need to find
environmentally friendly, but still effective, compounds with
antifouling effects.
Many new natural compounds are discovered every year, but
producing them on a large enough scale for commercial purposes is almost
impossible.
It is highly probable that future developments in this field will
rely on microorganisms, but greater funding and further research is
needed to overcome the lack of knowledge in this field.
Species groups
World capture fisheries and aquaculture production by main producers (2018), from
FAO's Statistical Yearbook 2020
Aquatic plants
Cultivating emergent aquatic plants in floating containers
Microalgae, also referred to as phytoplankton, microphytes, or planktonic algae, constitute the majority of cultivated algae. Macroalgae commonly known as seaweed
also have many commercial and industrial uses, but due to their size
and specific requirements, they are not easily cultivated on a large
scale and are most often taken in the wild.
In 2016, aquaculture was the source of 96.5 percent by volume of
the total 31.2 million tonnes of wild-collected and cultivated aquatic
plants combined. Global production of farmed aquatic plants,
overwhelmingly dominated by seaweeds, grew in output volume from 13.5
million tonnes in 1995 to just over 30 million tonnes in 2016.
Seaweed farming
A seaweed farmer in
Nusa Lembongan (Indonesia) gathers edible seaweed that has grown on a rope.
Seaweed farming or kelp farming is the practice of cultivating and harvesting seaweed.
In its simplest form, it consists of the management of naturally found
batches. In its most advanced form, it consists of fully controlling the
life cycle of the algae.
The top seven most cultivated seaweed taxa are Eucheuma spp., Kappaphycus alvarezii, Gracilaria spp., Saccharina japonica, Undaria pinnatifida, Pyropia spp., and Sargassum fusiforme. Eucheuma and K. alvarezii are farmed for carrageenan (a gelling agent); Gracilaria is farmed for agar;
while the rest are farmed for food. The largest seaweed-producing
countries are China, Indonesia, and the Philippines. Other notable
producers include South Korea, North Korea, Japan, Malaysia, and Zanzibar (Tanzania).
Seaweed farming has frequently been developed as an alternative to
improve economic conditions and to reduce fishing pressure and
overexploited fisheries.
Global production of farmed aquatic plants, overwhelmingly dominated by
seaweeds, grew in output volume from 13.5 million tonnes in 1995 to just
over 30 million tonnes in 2016. As of 2014, seaweed was 27% of all marine aquaculture. Seaweed farming is a
carbon negative crop, with a high potential for
climate change mitigation . The IPCC
Special Report on the Ocean and Cryosphere in a Changing Climate recommends "further research attention" as a mitigation tactic.
Fish
The farming of fish is the most common form of aquaculture. It involves raising fish commercially in tanks, fish ponds,
or ocean enclosures, usually for food. 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 used in fish farming are, in order, carp, salmon, tilapia, and catfish.
In the Mediterranean, young bluefin tuna are netted at sea and towed slowly towards the shore. They are then interned in offshore pens (sometimes made from floating HDPE pipe) where they are further grown for the market. In 2009, researchers in Australia managed for the first time to coax southern bluefin tuna to breed in landlocked tanks. Southern bluefin tuna are also caught in the wild and fattened in grow-out sea cages in southern Spencer Gulf, South Australia.
A similar process is used in the salmon-farming section of this
industry; juveniles are taken from hatcheries and a variety of methods
are used to aid them in their maturation. For example, as stated above,
some of the most important fish species in the industry, salmon, can be
grown using a cage system. This is done by having netted cages,
preferably in open water that has a strong flow, and feeding the salmon a
special food mixture that aids their growth. This process allows for
year-round growth of the fish, thus a higher harvest during the correct
seasons.
An additional method, known sometimes as sea ranching, has also been
used within the industry. Sea ranching involves raising fish in a hatchery
for a brief time and then releasing them into marine waters for further
development, whereupon the fish are recaptured when they have matured.
Crustaceans
Commercial shrimp
farming began in the 1970s, and production grew steeply thereafter.
Global production reached more than 1.6 million tonnes in 2003, worth
about US$9 billion. About 75% of farmed shrimp is produced in Asia, in
particular in China and Thailand. The other 25% is produced mainly in
Latin America, where Brazil is the largest producer. Thailand is the
largest exporter.
Shrimp farming has changed from its traditional, small-scale form
in Southeast Asia into a global industry. Technological advances have
led to ever higher densities per unit area, and broodstock is shipped worldwide. Virtually all farmed shrimp are penaeids (i.e., shrimp of the family Penaeidae), and just two species of shrimp, the Pacific white shrimp and the giant tiger prawn, account for about 80% of all farmed shrimp. These industrial monocultures are very susceptible to disease, which has decimated shrimp populations across entire regions. Increasing ecological problems, repeated disease outbreaks, and pressure and criticism from both nongovernmental organizations
and consumer countries led to changes in the industry in the late 1990s
and generally stronger regulations. In 1999, governments, industry
representatives, and environmental organizations initiated a program
aimed at developing and promoting more sustainable farming practices through the Seafood Watch program.
Freshwater prawn farming
shares many characteristics with, including many problems with, marine
shrimp farming. Unique problems are introduced by the developmental
lifecycle of the main species, the giant river prawn.
The global annual production of freshwater prawns (excluding crayfish and crabs) in 2007 was about 460,000 tonnes, exceeding 1.86 billion dollars. Additionally, China produced about 370,000 tonnes of Chinese river crab.
In addition astaciculture is the freshwater farming of crayfish (mostly in the US, Australia, and Europe).
Molluscs
Aquacultured shellfish include various oyster, mussel,
and clam species. These bivalves are filter and/or deposit feeders,
which rely on ambient primary production rather than inputs of fish or
other feed. As such, shellfish aquaculture is generally perceived as
benign or even beneficial.
Depending on the species and local conditions, bivalve molluscs
are either grown on the beach, on longlines, or suspended from rafts and
harvested by hand or by dredging. In May 2017 a Belgian consortium
installed the first of two trial mussel farms on a wind farm in the North Sea.
Abalone farming began in the late 1950s and early 1960s in Japan and China. Since the mid-1990s, this industry has become increasingly successful. Overfishing and poaching
have reduced wild populations to the extent that farmed abalone now
supplies most abalone meat. Sustainably farmed molluscs can be certified
by Seafood Watch and other organizations, including the World Wildlife Fund
(WWF). WWF initiated the "Aquaculture Dialogues" in 2004 to develop
measurable and performance-based standards for responsibly farmed
seafood. In 2009, WWF co-founded the Aquaculture Stewardship Council with the Dutch Sustainable Trade Initiative to manage the global standards and certification programs.
After trials in 2012, a commercial "sea ranch" was set up in Flinders Bay, Western Australia, to raise abalone. The ranch is based on an artificial reef made up of 5000 (As of April 2016) separate concrete units called abitats
(abalone habitats). The 900 kg abitats can host 400 abalone each. The
reef is seeded with young abalone from an onshore hatchery. The abalone
feed on seaweed that has grown naturally on the habitats, with the
ecosystem enrichment of the bay also resulting in growing numbers of
dhufish, pink snapper, wrasse, and Samson fish, among other species.
Brad Adams, from the company, has emphasised the similarity to
wild abalone and the difference from shore-based aquaculture. "We're not
aquaculture, we're ranching, because once they're in the water they
look after themselves."
Other groups
Other groups include aquatic reptiles, amphibians, and miscellaneous invertebrates, such as echinoderms and jellyfish.
They are separately graphed at the top right of this section, since
they do not contribute enough volume to show clearly on the main graph.
Commercially harvested echinoderms include sea cucumbers and sea urchins. In China, sea cucumbers are farmed in artificial ponds as large as 1,000 acres (400 ha).
Global fish production
Global
fish production peaked at about 171 million tonnes in 2016, with
aquaculture representing 47 percent of the total and 53 percent if
non-food uses (including reduction to fishmeal and fish oil) are
excluded. With capture fishery production relatively static since the
late 1980s, aquaculture has been responsible for the continuing growth
in the supply of fish for human consumption.
Global aquaculture production (including aquatic plants) in 2016 was
110.2 million tonnes, with the first-sale value estimated at US$243.5
billion. The contribution of aquaculture to the global production of
capture fisheries and aquaculture combined has risen continuously,
reaching 46.8 percent in 2016, up from 25.7 percent in 2000. With 5.8
percent annual growth rate during the period 2001–2016, aquaculture
continues to grow faster than other major food production sectors, but
it no longer has the high annual growth rates experienced in the 1980s
and 1990s.
In 2012, the total world production of fisheries was 158 million tonnes, of which aquaculture contributed 66.6 million tonnes, about 42%.
The growth rate of worldwide aquaculture has been sustained and rapid,
averaging about 8% per year for over 30 years, while the take from wild
fisheries has been essentially flat for the last decade. The aquaculture
market reached $86 billion in 2009.
Aquaculture is an especially important economic activity in
China. Between 1980 and 1997, the Chinese Bureau of Fisheries reports,
aquaculture harvests grew at an annual rate of 16.7%, jumping from 1.9
million tonnes to nearly 23 million tonnes. In 2005, China accounted for
70% of world production. Aquaculture is also currently one of the fastest-growing areas of food production in the U.S.
About 90% of all U.S. shrimp consumption is farmed and imported. In recent years, salmon aquaculture has become a major export in southern Chile, especially in Puerto Montt, Chile's fastest-growing city.
A United Nations report titled The State of the World Fisheries and Aquaculture released in May 2014 maintained fisheries and aquaculture support the livelihoods of some 60 million people in Asia and Africa.
FAO estimates that in 2016, overall, women accounted for nearly 14
percent of all people directly engaged in the fisheries and aquaculture
primary sector.
| Category
|
2011
|
2012
|
2013
|
2014
|
2015
|
2016
|
| Production
|
|
|
|
|
|
|
| Capture
|
|
|
|
|
|
|
| Inland
|
10.7
|
11.2
|
11.2
|
11.3
|
11.4
|
11.6
|
| Marine
|
81.5
|
78.4
|
79.4
|
79.9
|
81.2
|
79.3
|
| Total capture
|
92.2
|
89.5
|
90.6
|
91.2
|
92.7
|
90.9
|
| Aquaculture
|
|
|
|
|
|
|
| Inland
|
38.6
|
42
|
44.8
|
46.9
|
48.6
|
51.4
|
| Marine
|
23.2
|
24.4
|
25.4
|
26.8
|
27.5
|
28.7
|
| Total aquaculture
|
61.8
|
66.4
|
70.2
|
73.7
|
76.1
|
80
|
| Total world fisheries and aquaculture
|
154
|
156
|
160.7
|
164.9
|
168.7
|
170.9
|
| Utilization
|
|
|
|
|
|
|
| Human consumption
|
130
|
136.4
|
140.1
|
144.8
|
148.4
|
151.2
|
| Non-food uses
|
24
|
19.6
|
20.6
|
20
|
20.3
|
19.7
|
| Population (billions)
|
7
|
7.1
|
7.2
|
7.3
|
7.3
|
7.4
|
| Per capita apparent consumption (kg)
|
18.5
|
19.2
|
19.5
|
19.9
|
20.2
|
20.3
|
Over-reporting by China
China overwhelmingly dominates the world in reported aquaculture output,
reporting a total output which is double that of the rest of the world
put together. However, there are some historical issues with the
accuracy of China's returns.
In 2001, scientists Reg Watson and Daniel Pauly expressed concerns that China was over reporting its catch from wild fisheries in the 1990s.
They said that made it appear that the global catch since 1988 was
increasing annually by 300,000 tonnes, whereas it was really shrinking
annually by 350,000 tonnes. Watson and Pauly suggested this may be have
been related to Chinese policies where state entities that monitored the
economy were also tasked with increasing output. Also, until more
recently, the promotion of Chinese officials was based on production
increases from their own areas.
China disputed this claim. The official Xinhua News Agency
quoted Yang Jian, director general of the Agriculture Ministry's Bureau
of Fisheries, as saying that China's figures were "basically correct". However, the FAO
accepted there were issues with the reliability of China's statistical
returns, and for a period treated data from China, including the
aquaculture data, apart from the rest of the world.
Aquacultural methods
Mariculture
Carp are one of the dominant fishes in aquaculture The adaptable tilapia is another commonly farmed fish Mariculture refers to the cultivation of marine organisms in seawater,
usually in sheltered coastal or offshore waters. The farming of marine
fish is an example of mariculture, and so also is the farming of marine
crustaceans (such as shrimp), mollusks (such as oysters), and seaweed. Channel catfish (Ictalurus punctatus), hard clams (Mercenaria mercenaria) and Atlantic salmon (Salmo salar) are prominent in the U.S. mariculture.
Mariculture may consist of raising the organisms on or in
artificial enclosures such as in floating netted enclosures for salmon
and on racks for oysters. In the case of enclosed salmon, they are fed
by the operators; oysters on racks filter feed on naturally available
food. Abalone have been farmed on an artificial reef consuming seaweed
which grows naturally on the reef units.
Integrated
Integrated multi-trophic aquaculture (IMTA) is a practice in which the byproducts (wastes) from one species are recycled to become inputs (fertilizers, food) for another. Fed aquaculture (for example, fish, shrimp) is combined with inorganic extractive and organic extractive (for example, shellfish)
aquaculture to create balanced systems for environmental sustainability
(biomitigation), economic stability (product diversification and risk
reduction) and social acceptability (better management practices).
"Multi-trophic" refers to the incorporation of species from different trophic or nutritional levels in the same system. This is one potential distinction from the age-old practice of aquatic polyculture,
which could simply be the co-culture of different fish species from the
same trophic level. In this case, these organisms may all share the
same biological and chemical processes, with few synergistic benefits, which could potentially lead to significant shifts in the ecosystem. Some traditional polyculture systems may, in fact, incorporate a greater diversity of species, occupying several niches,
as extensive cultures (low intensity, low management) within the same
2006"/> A working IMTA system can result in greater total production
based on mutual benefits to the co-cultured species and improved ecosystem health, even if the production of individual species is lower than in a monoculture over a short-term period.
Sometimes the term "integrated aquaculture" is used to describe the integration of monocultures through water transfer.
For all intents and purposes, however, the terms "IMTA" and "integrated
aquaculture" differ only in their degree of descriptiveness. Aquaponics,
fractionated aquaculture, integrated agriculture-aquaculture systems,
integrated peri-urban-aquaculture systems, and integrated
fisheries-aquaculture systems are other variations of the IMTA concept.
Netting materials
Various materials, including nylon, polyester, polypropylene, polyethylene, plastic-coated welded wire, rubber, patented rope products (Spectra, Thorn-D, Dyneema), galvanized steel and copper are used for netting in aquaculture fish enclosures around the world. All of these materials are selected for a variety of reasons, including design feasibility, material strength, cost, and corrosion resistance.
Recently, copper alloys have become important netting materials in
aquaculture because they are antimicrobial (i.e., they destroy bacteria, viruses, fungi, algae, and other microbes) and they therefore prevent biofouling
(i.e., the undesirable accumulation, adhesion, and growth of
microorganisms, plants, algae, tubeworms, barnacles, mollusks, and other
organisms). By inhibiting microbial growth, copper alloy aquaculture
cages avoid costly net changes that are necessary with other materials.
The resistance of organism growth on copper alloy nets also provides a
cleaner and healthier environment for farmed fish to grow and thrive.
Issues
If performed without consideration for potential local environmental
impacts, aquaculture in inland waters can result in more environmental
damage than wild fisheries, though with less waste produced per kg on a global scale. Local concerns with aquaculture in inland waters may include waste handling, side-effects of antibiotics, competition between farmed and wild animals, and the potential introduction of invasive plant and animal species, or foreign pathogens, particularly if unprocessed fish are used to feed more marketable carnivorous
fish. If non-local live feeds are used, aquaculture may introduce
exotic plants or animals with disastrous effects. Improvements in
methods resulting from advances in research and the availability of
commercial feeds has reduced some of these concerns since their greater
prevalence in the 1990s and 2000s .
Fish waste is organic and composed of nutrients necessary in all
components of aquatic food webs. In-ocean aquaculture often produces
much higher than normal fish waste concentrations. The waste collects on
the ocean bottom, damaging or eliminating bottom-dwelling life. Waste can also decrease dissolved oxygen levels in the water column, putting further pressure on wild animals.
An alternative model to food being added to the ecosystem, is the
installation of artificial reef structures to increase the habitat
niches available, without the need to add any more than ambient feed and
nutrient. This has been used in the "ranching" of abalone in Western
Australia.
Impacts on wild fish
Some carnivorous and omnivorous farmed fish species are fed wild forage fish.
Although carnivorous farmed fish represented only 13 percent of
aquaculture production by weight in 2000, they represented 34 percent of
aquaculture production by value.
Farming of carnivorous species like salmon and shrimp leads to a
high demand for forage fish to match the nutrition they get in the wild.
Fish do not actually produce omega-3 fatty acids, but instead
accumulate them from either consuming microalgae that produce these fatty acids, as is the case with forage fish like herring and sardines, or, as is the case with fatty predatory fish, like salmon, by eating prey fish that have accumulated omega-3 fatty acids from microalgae. To satisfy this requirement, more than 50 percent of the world fish oil production is fed to farmed salmon.
Farmed salmon consume more wild fish
than they generate as a final product, although the efficiency of
production is improving. To produce one pound of farmed salmon, products
from several pounds of wild fish are fed to them - this can be
described as the "fish-in-fish-out" (FIFO) ratio. In 1995, salmon had a
FIFO ratio of 7.5 (meaning 7.5 pounds of wild fish feed were required to
produce 1 pound of salmon); by 2006 the ratio had fallen to 4.9.
Additionally, a growing share of fish oil and fishmeal come from
residues (byproducts of fish processing), rather than dedicated whole
fish. In 2012, 34 percent of fish oil and 28 percent of fishmeal came from residues.
However, fishmeal and oil from residues instead of whole fish have a
different composition with more ash and less protein, which may limit
its potential use for aquaculture.
As the salmon farming industry expands, it requires more wild
forage fish for feed, at a time when seventy-five percent of the world's
monitored fisheries are already near to or have exceeded their maximum sustainable yield.
The industrial-scale extraction of wild forage fish for salmon farming
then impacts the survivability of the wild predator fish who rely on
them for food. An important step in reducing the impact of aquaculture
on wild fish is shifting carnivorous species to plant-based feeds.
Salmon feeds, for example, have gone from containing only fishmeal and
oil to containing 40 percent plant protein. The USDA has also experimented with using grain-based feeds for farmed trout.
When properly formulated (and often mixed with fishmeal or oil),
plant-based feeds can provide proper nutrition and similar growth rates
in carnivorous farmed fish.
Another impact aquaculture production can have on wild fish is
the risk of fish escaping from coastal pens, where they can interbreed
with their wild counterparts, diluting wild genetic stocks. Escaped fish can become invasive, out-competing native species.
Animal welfare
As with the farming of terrestrial animals, social attitudes
influence the need for humane practices and regulations in farmed marine
animals. Under the guidelines advised by the Farm Animal Welfare Council
good animal welfare means both fitness and a sense of well-being in the
animal's physical and mental state. This can be defined by the Five Freedoms:
- Freedom from hunger & thirst
- Freedom from discomfort
- Freedom from pain, disease, or injury
- Freedom to express normal behaviour
- Freedom from fear and distress
However, the controversial issue in aquaculture is whether fish and farmed marine invertebrates are actually sentient,
or have the perception and awareness to experience suffering. Although
no evidence of this has been found in marine invertebrates, recent studies conclude that fish do have the necessary receptors (nociceptors) to sense noxious stimuli and so are likely to experience states of pain, fear and stress. Consequently, welfare in aquaculture is directed at vertebrates; finfish in particular.
Common welfare concerns
Welfare in aquaculture can be impacted by a number of issues such as stocking densities, behavioural interactions, disease and parasitism.
A major problem in determining the cause of impaired welfare is that
these issues are often all interrelated and influence each other at
different times.
Optimal stocking density is often defined by the carrying capacity
of the stocked environment and the amount of individual space needed by
the fish, which is very species specific. Although behavioural
interactions such as shoaling may mean that high stocking densities are beneficial to some species,
in many cultured species high stocking densities may be of concern.
Crowding can constrain normal swimming behaviour, as well as increase
aggressive and competitive behaviours such as cannibalism, feed competition, territoriality and dominance/subordination hierarchies. This potentially increases the risk of tissue damage due to abrasion from fish-to-fish contact or fish-to-cage contact. Fish can suffer reductions in food intake and food conversion efficiency.
In addition, high stocking densities can result in water flow being
insufficient, creating inadequate oxygen supply and waste product
removal. Dissolved oxygen is essential for fish respiration and concentrations below critical levels can induce stress and even lead to asphyxiation.
Ammonia, a nitrogen excretion product, is highly toxic to fish at
accumulated levels, particularly when oxygen concentrations are low.
Many of these interactions and effects cause stress in the fish, which can be a major factor in facilitating fish disease.
For many parasites, infestation depends on the host's degree of
mobility, the density of the host population and vulnerability of the
host's defence system.
Sea lice are the primary parasitic problem for finfish in aquaculture,
high numbers causing widespread skin erosion and haemorrhaging, gill
congestion, and increased mucus production. There are also a number of prominent viral and bacterial pathogens that can have severe effects on internal organs and nervous systems.
Improving welfare
The
key to improving welfare of marine cultured organisms is to reduce
stress to a minimum, as prolonged or repeated stress can cause a range
of adverse effects. Attempts to minimise stress can occur throughout the
culture process. Understanding and providing required environmental
enrichment can be vital for reducing stress and benefit aquaculture
objects such as improved growth body condition and reduced damage from
aggression.
During grow-out it is important to keep stocking densities at
appropriate levels specific to each species, as well as separating size
classes and grading to reduce aggressive behavioural interactions.
Keeping nets and cages clean can assist positive water flow to reduce
the risk of water degradation.
Not surprisingly disease and parasitism can have a major effect
on fish welfare and it is important for farmers not only to manage
infected stock but also to apply disease prevention measures. However,
prevention methods, such as vaccination, can also induce stress because
of the extra handling and injection.
Other methods include adding antibiotics to feed, adding chemicals into
water for treatment baths and biological control, such as using cleaner wrasse to remove lice from farmed salmon.
Many steps are involved in transport, including capture, food
deprivation to reduce faecal contamination of transport water, transfer
to transport vehicle via nets or pumps, plus transport and transfer to
the delivery location. During transport water needs to be maintained to a
high quality, with regulated temperature, sufficient oxygen and minimal
waste products. In some cases anaesthetics may be used in small doses to calm fish before transport.
Aquaculture is sometimes part of an environmental rehabilitation program or as an aid in conserving endangered species.
Coastal ecosystems
Aquaculture is becoming a significant threat to coastal ecosystems. About 20 percent of mangrove forests have been destroyed since 1980, partly due to shrimp farming. An extended cost–benefit analysis of the total economic value of shrimp aquaculture built on mangrove ecosystems found that the external costs were much higher than the external benefits.
Over four decades, 269,000 hectares (660,000 acres) of Indonesian
mangroves have been converted to shrimp farms. Most of these farms are
abandoned within a decade because of the toxin build-up and nutrient loss.
Pollution from sea cage aquaculture
Salmon aquaculture, Norway
Salmon farms
are typically sited in pristine coastal ecosystems which they then
pollute. A farm with 200,000 salmon discharges more fecal waste than a
city of 60,000 people. This waste is discharged directly into the
surrounding aquatic environment, untreated, often containing antibiotics
and pesticides." There is also an accumulation of heavy metals on the benthos (seafloor) near the salmon farms, particularly copper and zinc.
In 2016, mass fish kill events impacted salmon farmers along Chile's coast and the wider ecology.
Increases in aquaculture production and its associated effluent were
considered to be possible contributing factors to fish and molluscan
mortality.
Sea cage aquaculture is responsible for nutrient enrichment of
the waters in which they are established. This results from fish wastes
and uneaten feed inputs. Elements of most concern are nitrogen and
phosphorus which can promote algal growth, including harmful algal
blooms which can be toxic to fish. Flushing times, current speeds,
distance from the shore and water depth are important considerations
when locating sea cages in order to minimize the impacts of nutrient
enrichment on coastal ecosystems.
The extent of the effects of pollution from sea-cage aquaculture
varies depending on where the cages are located, which species are kept,
how densely cages are stocked and what the fish are fed. Important
species-specific variables include the species' food conversion ratio
(FCR) and nitrogen retention.
Freshwater ecosystems
Whole-lake experiments carried out at the Experimental Lakes Area
in Ontario, Canada have displayed the potential for cage aquaculture to
source numerous changes in freshwater ecosystems. Following the
initiation of an experimental rainbow trout cage farm in a small boreal lake, dramatic reductions in mysis concentrations associated with a decrease in dissolved oxygen were observed. Significant increases in ammonium and total phosphorus, a driver for eutrophication in freshwater systems, were measured in the hypolimnion
of the lake. Annual phosphorus inputs from aquaculture waste exceeded
that of natural inputs from atmospheric deposition and inflows, and phytoplankton biomass has had a fourfold annual increase following the initiation of the experimental farm.
Genetic modification
A type of salmon called the AquAdvantage salmon has been genetically modified for faster growth, although it has not been approved for commercial use, due to controversy. The altered salmon incorporates a growth hormone from a Chinook salmon
that allows it to reach full size in 16–28 months, instead of the
normal 36 months for Atlantic salmon, and while consuming 25 percent
less feed.
The U.S. Food and Drug Administration reviewed the AquAdvantage salmon
in a draft environmental assessment and determined that it "would not
have a significant impact (FONSI) on the U.S. environment."
Fish diseases, parasites and vaccines
A major difficulty for aquaculture is the tendency towards monoculture and the associated risk of widespread disease. Aquaculture is also associated with environmental risks; for instance, shrimp farming has caused the destruction of important mangrove forests throughout southeast Asia.
In the 1990s, disease wiped out China's farmed Farrer's scallop and white shrimp and required their replacement by other species.
Needs of the aquaculture sector in vaccines
Aquaculture
has an average annual growth rate of 9.2%, however the success and
continued expansion of the fish farming sector is highly dependent on
the control of fish pathogens including a wide range of viruses,
bacteria, fungi, and parasites. In 2014, it was estimated that these
parasites cost the global salmon farming industry up to 400 million
Euros. This represents 6-10% of the production value of the affected
countries, but it can go up to 20% (Fisheries and Oceans Canada, 2014).
Since pathogens quickly spread within a population of cultured fish,
their control is vital for the sector.
Historically, the use of antibiotics was against bacterial epizootics
but production of animal proteins has to be sustainable, which means
that preventive measures that are acceptable from a biological and
environmental point of view should be used to keep disease problems in
aquaculture at an acceptable level. So, this added to the efficiency of
vaccines resulted in an immediate and permanent reduction in the use of
antibiotics in the 90s. At the beginning there were fish immersion
vaccines efficient against the vibriosis but proved ineffective against
the furunculosis, hence the arrival of injectable vaccines: first
water-based and after oil-based, much more efficient (Sommerset, 2005).
Development of new vaccines
It
is the important mortality in cages among farmed fish, the debates
around DNA injection vaccines, although effective, their safety and
their side effects but also societal expectations for cleaner fish and
security, lead research on new vaccine vectors. Several initiatives are
financed by the European Union to develop a rapid and cost-effective
approach to using bacteria in feed to make vaccines, in particular
thanks to lactic bacteria whose DNA is modified (Boudinot, 2006). In
fact, vaccinating farmed fish by injection is time-consuming and costly,
so vaccines can be administered orally or by immersion by being added
to feed or directly into water. This allows to vaccinate many
individuals at the same time, while limiting the associated handling and
stress.
Indeed, many tests are necessary because the antigens of the vaccines
must be adapted to each species or not present a certain level of
variability or they will not have any effect. For example, tests have
been done with 2 species: Lepeophtheirus salmonis (from which the
antigens were collected) and Caligus rogercresseyi (which was vaccinated
with the antigens), although the homology between the two species is
important, the level of variability made the protection ineffective
(Fisheries and Oceans Canada, 2014).
Recent vaccines development in aquaculture
There
are 24 vaccines available and one for lobsters. The first vaccine was
used in the USA against enteric red mouth in 1976. However, there are 19
companies and some small stakeholders are producing vaccines for
aquaculture nowadays. The novel approaches are a way forward to prevent
the loss of 10% aquaculture through disease. Genetically modified
vaccines are not being used in the EU due to societal concerns and
regulations. Meanwhile, DNA vaccines are now authorised in the EU
(Adams, 2019).
There are challenges in fish vaccine development, immune response due to
lack of potent adjScientists are considering microdose application in
future. But there are also exciting opportunities in aquaculture
vaccinology due to low cost of technology, regulations change and novel
antigen expression and delivery systems.
In Norway subunit vaccine (VP2 peptide) against infectious pancreatic
necrosis is being used. In Canada, a licensed DNA vaccine against
Infectious hematopoietic necrosis has been launched for industry use.
Fish have large mucosal surfaces, so the preferred route is immersion,
intraperitoneal and oral respectively. Nanoparticles are under progress
for delivery purposes. The common antibodies produced are IgM and IgT.
Normally booster is not required ifn Fish because more memory cells are
produced in response to booster rather than increased level of
antibodies.
mRNA vaccines are alternative to DNA vaccines because they are more
safe, stable, easily producible at large scale and mass immunization
potential. Recently these are used in cancer prevention and
therapeutics. Studies in rabies has shown that efficacy depends on dose
and route of administration. These are still in infancy (Adams, 2019).
Economic gains
In
2014, the aquaculture produced fish overtook wild caught fish, in
supply for human food. This means there is a huge demand for vaccines,
in prevention of diseases. The reported annual loss fish, calculates to
>10 billion usd. This is from approximately 10% of all fishes dying
from infectious diseases. (Adams, 2019).
The high annual losses increases the demand for vaccines. Even though
there are about 24 traditionally used vaccines, there is still demand
for more vaccines. The breakthrough of DNA-vaccines has sunk the cost of
vaccines (Adams, 2019).
The alternative to vaccines would be antibiotics and
chemotherapy, which are more expensive and with bigger drawbacks.
DNA-vaccines have become the most cost-efficient method of preventing
infectious diseases. This bouts well for DNA-vaccines becoming the new
standard both in fish vaccines, and in general vaccines (Ragnar
Thorarinsson, 2021).
Salinization/acidification of soils
Sediment from abandoned aquaculture farms can remain hypersaline, acidic
and eroded. This material can remain unusable for aquaculture purposes
for long periods thereafter. Various chemical treatments, such as adding
lime, can aggravate the problem by modify the physicochemical characteristics of the sediment.
Ecological benefits
While
some forms of aquaculture can be devastating to ecosystems, such as
shrimp farming in mangroves, other forms can be very beneficial.
Shellfish aquaculture adds substantial filter feeding capacity to an
environment which can significantly improve water quality. A single
oyster can filter 15 gallons of water a day, removing microscopic algal
cells. By removing these cells, shellfish are removing nitrogen and
other nutrients from the system and either retaining it or releasing it
as waste which sinks to the bottom. By harvesting these shellfish the
nitrogen they retained is completely removed from the system.
Raising and harvesting kelp and other macroalgae directly remove
nutrients such as nitrogen and phosphorus. Repackaging these nutrients
can relieve eutrophic, or nutrient-rich, conditions known for their low
dissolved oxygen which can decimate species diversity and abundance of
marine life. Removing algal cells from the water also increases light
penetration, allowing plants such as eelgrass to reestablish themselves
and further increase oxygen levels.
Aquaculture in an area can provide for crucial ecological
functions for the inhabitants. Shellfish beds or cages can provide
habitat structure. This structure can be used as shelter by
invertebrates, small fish or crustaceans to potentially increase their
abundance and maintain biodiversity. Increased shelter raises stocks of
prey fish and small crustaceans by increasing recruitment opportunities
in turn providing more prey for higher trophic levels. One study
estimated that 10 square meters of oyster reef could enhance an
ecosystem's biomass by 2.57 kg
The shellfish acting as herbivores will also be preyed on. This moves
energy directly from primary producers to higher trophic levels
potentially skipping out on multiple energetically-costly trophic jumps
which would increase biomass in the ecosystem.
Seaweed farming is a carbon negative crop, with a high potential for climate change mitigation. The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate recommends "further research attention" as a mitigation tactic.
Regenerative ocean farming is a polyculture farming system that grows a
mix of seaweeds and shellfish while sequestering carbon, decreasing
nitrogen in the water and increasing oxygen, helping to regenerate and
restore local habitat like reef ecosystems.
Prospects
Global wild fisheries are in decline, with valuable habitat such as estuaries in critical condition. The aquaculture or farming of piscivorous fish, like salmon, does not help the problem because they need to eat products from other fish, such as fish meal and fish oil. Studies have shown that salmon farming has major negative impacts on wild salmon, as well as the forage fish that need to be caught to feed them. Fish that are higher on the food chain are less efficient sources of food energy.
Apart from fish and shrimp, some aquaculture undertakings, such as seaweed and filter-feeding bivalve mollusks like oysters, clams, mussels and scallops, are relatively benign and even environmentally restorative. Filter-feeders filter pollutants as well as nutrients from the water, improving water quality. Seaweeds extract nutrients such as inorganic nitrogen and phosphorus directly from the water, and filter-feeding mollusks can extract nutrients as they feed on particulates, such as phytoplankton and detritus.
Some profitable aquaculture cooperatives promote sustainable practices. New methods lessen the risk of biological and chemical pollution through minimizing fish stress, fallowing netpens, and applying Integrated Pest Management. Vaccines are being used more and more to reduce antibiotic use for disease control.
Onshore recirculating aquaculture systems, facilities using polyculture
techniques, and properly sited facilities (for example, offshore areas
with strong currents) are examples of ways to manage negative
environmental effects.
Recirculating aquaculture systems
(RAS) recycle water by circulating it through filters to remove fish
waste and food and then recirculating it back into the tanks. This saves
water and the waste gathered can be used in compost
or, in some cases, could even be treated and used on land. While RAS
was developed with freshwater fish in mind, scientists associated with
the Agricultural Research Service have found a way to rear saltwater fish using RAS in low-salinity waters. Although saltwater fish are raised in off-shore cages or caught with nets in water that typically has a salinity of 35 parts per thousand
(ppt), scientists were able to produce healthy pompano, a saltwater
fish, in tanks with a salinity of only 5 ppt. Commercializing
low-salinity RAS are predicted to have positive environmental and
economical effects. Unwanted nutrients from the fish food would not be
added to the ocean and the risk of transmitting diseases between wild
and farm-raised fish would greatly be reduced. The price of expensive
saltwater fish, such as the pompano and combia used in the experiments,
would be reduced. However, before any of this can be done researchers
must study every aspect of the fish's lifecycle, including the amount of
ammonia and nitrate the fish will tolerate in the water, what to feed
the fish during each stage of its lifecycle, the stocking rate that will produce the healthiest fish, etc.
Some 16 countries now use geothermal energy for aquaculture, including China, Israel, and the United States.
In California, for example, 15 fish farms produce tilapia, bass, and
catfish with warm water from underground. This warmer water enables fish
to grow all year round and mature more quickly. Collectively these
California farms produce 4.5 million kilograms of fish each year.
National laws, regulations, and management
Laws governing aquaculture practices vary greatly by country and are often not closely regulated or easily traceable.
In the United States, land-based and nearshore aquaculture is regulated at the federal and state levels; however, no national laws govern offshore aquaculture in U.S. exclusive economic zone waters. In June 2011, the Department of Commerce and National Oceanic and Atmospheric Administration released national aquaculture policies
to address this issue and "to meet the growing demand for healthy
seafood, to create jobs in coastal communities, and restore vital
ecosystems." Large aquaculture facilities (i.e. those producing 20,000
pounds (9,100 kg) per year) which discharge wastewater are required to obtain permits pursuant to the Clean Water Act.
Facilities that produce at least 100,000 pounds (45,000 kg) of fish,
molluscs or crustaceans a year are subject to specific national
discharge standards. Other permitted facilities are subject to effluent limitations that are developed on a case-by-case basis.
History
Workers harvest catfish from the Delta Pride Catfish farms in Mississippi
The Gunditjmara, the local Aboriginal Australian people in south-western Victoria, Australia, may have raised short-finned eels as early as about 4,580 BCE. Evidence indicates they developed about 100 km2 (39 sq mi) of volcanic floodplains in the vicinity of Lake Condah into a complex of channels and dams, and used woven traps to capture eels, and preserve them to eat all year round. The Budj Bim Cultural Landscape, a World Heritage Site, is thought to be one of the oldest aquaculture sites in the world.
Oral tradition in China tells of the culture of the common carp, Cyprinus carpio, as long ago as 2000–2100 BCE (around 4,000 years BP), but the earliest significant evidence lies in the literature, in the earliest monograph on fish culture called The Classic of Fish Culture, by Fan Li, written around 475 BCE (c.2475 BP). Another ancient Chinese guide to aquaculture was by Yang Yu Jing, written around 460 BCE, showing that carp farming was becoming more sophisticated. The Jiahu site in China has circumstantial archeological evidence as possibly the oldest aquaculture locations, dating from 6200BCE (about 8,200 years BP), but this is speculative. When the waters subsided after river floods, some fish, mainly carp, were trapped in lakes. Early aquaculturists fed their brood using nymphs and silkworm faeces, and ate them.
Ancient Egyptians might have farmed fish (especially Gilt-head bream) from Lake Bardawil about 1,500 BCE (3,520 years BP), and they traded them with Canaan.
Gim cultivation is the oldest aquaculture in Korea. Early cultivation methods used bamboo or oak sticks, which were replaced by newer methods that utilized nets in the 19th century. Floating rafts have been used for mass production since the 1920s.
Japanese cultivated seaweed by providing bamboo poles and, later, nets and oyster shells to serve as anchoring surfaces for spores.
Romans bred fish in ponds and farmed oysters in coastal lagoons before 100 CE.
In central Europe, early Christian monasteries adopted Roman aquacultural practices. Aquaculture spread in Europe during the Middle Ages since away from the seacoasts and the big rivers, fish had to be salted so they did not rot.
Improvements in transportation during the 19th century made fresh fish
easily available and inexpensive, even in inland areas, making
aquaculture less popular. The 15th-century fishponds of the Trebon Basin in the Czech Republic are maintained as a UNESCO World Heritage Site.
Hawaiians constructed oceanic fish ponds. A remarkable example is the "Menehune" fishpond dating from at least 1,000 years ago, at Alekoko. Legend says that it was constructed by the mythical Menehune dwarf people.
In the first half of the 18th century, German Stephan Ludwig Jacobi experimented with external fertilization of brown trouts and salmon. He wrote an article "Von der künstlichen Erzeugung der Forellen und Lachse" (On the Artificial Production of Trout and Salmon) summarizing his findings, and is regarded as the founder of artificial fish rearing in Europe. By the latter decades of the 18th century, oyster farming had begun in estuaries along the Atlantic Coast of North America.
The word aquaculture appeared in an 1855 newspaper article in reference to the harvesting of ice. It also appeared in descriptions of the terrestrial agricultural practise of sub-irrigation in the late 19th century before becoming associated primarily with the cultivation of aquatic plant and animal species.
In 1859, Stephen Ainsworth of West Bloomfield, New York, began experiments with brook trout. By 1864, Seth Green had established a commercial fish-hatching operation at Caledonia Springs, near Rochester, New York. By 1866, with the involvement of Dr. W. W. Fletcher of Concord, Massachusetts, artificial fish hatcheries were underway in both Canada and the United States. When the Dildo Island
fish hatchery opened in Newfoundland in 1889, it was the largest and
most advanced in the world. The word aquaculture was used in
descriptions of the hatcheries experiments with cod and lobster in 1890.
By the 1920s, the American Fish Culture Company of Carolina, Rhode Island,
founded in the 1870s was one of the leading producers of trout. During
the 1940s, they had perfected the method of manipulating the day and
night cycle of fish so that they could be artificially spawned year
around.
Californians harvested wild kelp and attempted to manage supply around 1900, later labeling it a wartime resource.
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