WHAT IS
AQUACULTURE?
Aquaculture is also known as fish or shellfish farming refers
to the breeding, rearing, and harvesting of plants and animals in all types of
water environments including ponds, rivers, lakes, and the ocean. Researchers and aquaculture producers are "farming" all kinds
of freshwater and marine species of fish, shellfish, and plants.
Aquaculture produces food fish, sport fish, bait fish, ornamental fish,
crustaceans, mollusks, algae, sea vegetables, and fish eggs.Aquaculture
includes the production of seafood from hatchery fish and shellfish which are
grown to market size in ponds, tanks, cages, or raceways. Stock
restoration or "enhancement" is a form of aquaculture in which
hatchery fish and shellfish are released into the wild to rebuild wild
populations or coastal habitats such as oyster reefs.
Aquaculture also
includes the production of ornamental fish for the aquarium trade, and growing
plant species used in a range of food, pharmaceutical, nutritional, and
biotechnology products.
Marine aquaculture refers to the culturing of
species that live in the ocean. U.S. marine aquaculture primarily
produces oysters, clams, mussels, shrimp, and salmon as well as lesser amounts
of cod, moi, yellowtail, barramundi, seabass, and sea bream. Marine
aquaculture can take place in the ocean (that is, in cages, on the seafloor, or
suspended in the water column) or in on-land, manmade systems such as ponds or
tanks. Recirculating aquaculture systems that reduce, reuse, and recycle
water and waste can support some marine species.
Freshwater aquaculture produces species that are
native to rivers, lakes, and streams. U.S. freshwater aquaculture is
dominated by catfish but also produces trout, tilapia, and bass.
Freshwater aquaculture takes place primarily in ponds and in
on-land, manmade systems such as recirculating aquaculture systems. As the
nation's oceans agency, NOAA and its Office of Aquaculture focus on marine
aquaculture, although research and advancement in technology can be more
broadly applied. Continued advances in technology and management
practices are expanding aquaculture's potential role in producing a variety of
species for both restoration and commercial purposes.
History of aquaculture
The cultivation of marine
species is also an ancient practice. Ancient Chinese manuscripts from the 5th
century B.C. indicate the Chinese practiced fish culture. Although not as
implicit, Egyptian hieroglyphics indicate the Egyptians of the Middle Kingdom
(2052-1786 B.C.) attempted intensive fish culturing. Following in the footsteps
of the Egyptians, the Romans also developed aquaculture practices as they are
known to have cultivated oysters. The culture of oysters established by the
Romans is the first known form of aquaculture that has continued in some form
or another to the modern day.
All of the early forms of
aquaculture differed greatly from much of the aquaculture practiced today. The
major difference is that aquaculture in ancient times involved harvesting
immature fish or shellfish and transferring them to an artificially created
environment that is favorable to their growth. Carp, in China, thousands of
years ago were collected as youngsters and transferred to special ponds where
they were grown. As the Egyptians and Romans proved this practice was not
limited to carp but was used with many other species such as oysters and other
hardy creatures capable of surviving the transfer to the culture ponds.
Fish farming in its modern
form was first introduced in 1733 when a German farmer successfully gathered
fish eggs, fertilized them, and then grew and raised the fish that hatched. To
do this, male and female trout were collected when they were ready for
spawning. The eggs and sperm were pressed from their bodies and mixed under
favorable conditions. After hatching, the fish lings were taken to tanks or
ponds in which they were cultivated. Initially this "fish farming"
was limited to freshwater fish. In the 20th century new techniques were
developed to successfully breed saltwater species.
As scientists have learned
more about the life cycles of the harvested fish and the stimuli that encourage
development, fish farmers are adapting their techniques to gain more control
over the fishes’ development. Such factors that are important to commercial
fish farmers are the stimuli that encourage growth, sexual maturation, and reproduction.
Other recent advances include disease control and immunology.
For most of the history of
modern aquaculture, only luxury items such as salmon and shrimp were harvested.
That trend is changing as new technologies allow for efficient and cost effective
cultivation of non-luxury cheap food fish.
Aquaculture around the
world
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.[55] In recent years, salmon aquaculture
has become a major export in southern Chile, especially in Puerto
Montt, Chile's fastest-growing city.
Issues related to aquaculture
farming
If performed without consideration for
potential local environmental impacts, aquaculture in inland waters can result
in more environmental damaging than wild fisheries, though with less waste
produced on a 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 plant of animal. 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 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.[79] 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.
Fish Oil
Further
information: Tilapia
§ Nutrition
Tilapia from aquaculture has been shown
to contain more fat and a much higher ratio of omega-6 to omega-3 oils.
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 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.
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 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."[7] 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 mollucs can 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. Studies prior to 2001 determined that the
amount of nitrogen introduced as feed which is lost to the water column and
seafloor as waste varies from 52 to 95%.
Modification of genetics
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.
