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Note:
words in red link
to an online glossary (or
dictionary) of related terms.
Introduction
Aquaculture is the art, science, and business of producing
aquatic plants and animals for human use in a controlled environment.
Given our highly health-conscious society and the declining wild
fish populations, there is a vital need for aquaculture, which
produces reliable, high -quality protein such as fish, shellfish
and plants for consumers.
Aquaculture, like agriculture,
is the cultivation and harvest of plants and animals for human
use. Both aquaculture, and agriculture
are farming, but aquaculture — farming in water — requires
a different set of knowledge, skills and technology. Plants and
animals are held in water in a variety of systems, fed continuously,
harvested and sold to distributors.
Fish farming is rapidly expanding in the United States and in New
England in particular. Wide ranges of species are being grown nationally,
with catfish most popular in the South, and salmon and oysters
dominating the Northeast.
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History
of Aquaculture
Aquaculture has been around for centuries, in one form or another,
all over the world. Chinese manuscripts from the 5th century B.C.
indicate that the Chinese practiced fish culture in ponds.1 They
raised mud carp, which feed on plants and animals from the bottom,
silver carp which feed on phytoplankton and zooplankton, and grass
carp which feed on floating aquatic plants.2 This method allowed
for efficient use of the ponds. The fish were captured from the wild
when they were still juveniles and then raised in the ponds to adulthood.
Like the Chinese, the ancient Egyptians may have raised fish in small
ponds. Ponds that seem to contain intensive fish culturing have shown
up in Egyptian hieroglyphics.1 The ancient Romans followed in the
Egyptian footsteps by culturing mussels in small ponds.1 Aquaculture
occurred in Japan, for pearls, Indonesia, for brackish water fish,
and even in Medieval Europe, where people would catch small fish
and put them in moats to fatten.2 In all of these cases, fish were
captured as juveniles and then raised to maturity to be eaten. If
the fish spawned and reproduced, it was a side effect rather than
the goal.2
It was during the mid-16th century that modern aquaculture began.
In 1733, a German farmer gathered trout eggs, fertilized them, hatched
them, and then grew the larvae to adulthood.1 Early modern aquaculture
was limited to salmon, shrimp, and more luxury seafood, but as it
became more economical, more common species began to emerge in fish
farms.1 During the Depression, American aquaculture got a push forward
with the “Farm Pond” program, which was part of the New
Deal. Farmers were assisted by the government in the construction
and stocking of farms in an attempt to increase their income.2 Trout
has been cultured commonly since the 1950s as a recreational fish
to restock ponds and rivers.3
Currently, there are 20 species commonly cultured in the United States
and 100 species cultured worldwide.3 Research conducted at the MIT
Sea Grant Finfish Hatchery and similar hatcheries is attempting to
increase that number to reduce our dependence on wild stocks.
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to Top Types
of Aquaculture
Depending
on the requirements of the species, the animals or plants can
be raised in a warm, cold or marine environment.
In warm fresh
water, catfish, crayfish, baitfish, sportfish, tilapia and ornamental
fish are grown.
Cold fresh water trout and salmon are grown. In mariculture, which uses brackish
or salt water, brackish clams, oysters, seaweed, mussels, shrimp, haddock,
cod, salmon, and flounder are grown.
Each life
stage of these species can take place in several different growing
environments. Depending on the species being cultured and well
as the location of the facility ponds, tanks, open ocean, raceways,
or cages would be choices for rearing systems.
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Aquaculture
Systems
Aquaculture occurs in three different forms: ponds, pens, and
recirculating tanks. Pond aquaculture is most like farming. With
this method, areas of land are enclosed by dikes and flooded. Fish,
most commonly catfish or shrimp, are then added to the pond. The
fish or shellfish are fed on a regular schedule, and a clean source
of water is used to keep the pond in the proper condition for healthy
growth.
Floating
pens are the most common methods for growing marine finfish,
such as salmon, in protected coastal waters. One of the biggest
concerns in aquaculture is continuously providing fresh, clean
water for the fish. In large enclosures made of netting, fish
can enjoy a natural flow of water and all the food they can eat.
This open-water approach is also used in growing marine shellfish,
with the natural currents bringing both clean water and plenty
of food for filter-feeding bivalves such as oysters, quahogs,
and scallops.
The open ocean method of aquaculture is similar to the pens, but
consists of pens located offshore. One advantage to culturing fish
offshore is that pens can be located on sites that are not already
being used for recreation or fishing. The fish are fed on a regular
schedule, while shellfish are provided with plenty of food by the
natural currents. Commercial fishing vessels can transport or harvest
the fish, which creates more jobs within a community currently
struggling to support itself. The
newest kind of aquaculture employs recirculating systems to clean
and re-use water. "Recirc" systems are made up of several
components that filter the culture water of waste and toxins
and treat it to reduce the bacteria and virus load. Because one
can control the environmental parameters in this recycling system,
growers can carefully control water quality, and “recirc” systems
eliminate the risk of weather-dependent ponds and pens. Recirculating
systems also use far less water than other methods and any discharge
water can be thoroughly treated to make sure that no waste is
released into public waters. Check out this animated recirculating
system.
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Many
kinds of plants and animals are grown
Freshwater |
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Varied waters |
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Saltwater |
Ornamental
Striped Bass |
catfish |
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Red
Drum |
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Hydroponic
seaweed |
Hydroponic
lettuce |
Trout |
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Shrim |
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Crawfish |
Hydroponic
spices |
Tilapia |
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Shellfish |
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winter flounder |
Tilapia |
Yellow
Perch |
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Salmon |
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Shrimp |
Baitfish |
Walleye |
|
Yellow
Perch |
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Shellfish |
Hydroponic
seaweed |
Baitfish |
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Back
to Top Aquaculture
and the Environment
Aquaculture, like agriculture is the cultivation and harvest
of plants and animals for human use. Both are farming, but aquaculture – farming
in water – requires a different set of knowledge, skills and
technology. Just like agriculture, aquaculture comes in many different
forms, with different environmental effects. Aquaculturists are working
to reduce any negative effects that fish farms may have.
Pond aquaculture, which is most commonly used to cultivate shellfish,
consists of pens that are placed in rivers or estuaries.4 Water
flow and feed for these pens come from the natural sources available.5
These pens can change the flow patterns and speeds within the pens.4 However, the farms can help reduce the over-enrichment of many
coastal waters due to runoff from agriculture and human activities,
which improves the quality of the water and the wild populations.6
Recirculating
aquaculture systems are used to cultivate many different types
of fish and plants. These systems use a filtration system
to clean and re-use the water, and the fish are fed with artificial
food sources.5 Because this type of aquaculture is mainly self-contained
and can control what it outputs, it has a limited environmental
impact. The fish are raised at high densities, making them economical.
Pen culture, occurring in the open ocean, depends on natural
water
flows and artificial feed. The fish, most commonly salmon, are
cultured at a high density, which can cause problems with disease
and parasites.7 When antibiotics are included in the food to treat
disease, the wild animals in the area, especially bottom feeders,
can consume the chemicals in the excess food.7 However, antibiotics
are now administered individually, and pens are isolated while
the fish are being treated. 5
One environmental concern common to the systems that use artificial
feed is a dependency on baitfish for the fishmeal. Fishmeal is
used in the production of food for fish, dogs, cats, and several
farm animals. Because using fishmeal for the increasing volume
of pet food can put stress on the wild stock, research is being
conducted on the use of soy products to replace the fishmeal.
An environmental concern common to the systems that use natural
water flows is eutrophication due to excess feed and waste. Eutrophication is the process by which a body of water can become enriched in
dissolved nutrients, promoting algal growth.8 It is a problem because
an excess of nutrients degrades the water quality, and creates
an imbalance in the food web.8 Culturing plants near the pens that
feed on the nutrients that the fish give off as waste helps the
problem, as does treatment similar to that at a sewage treatment
plant. 8
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Aquaculture
and Commercial Fishing
Some people are concerned that aquaculture will take away jobs
and income from commercial fishermen. This is not the case. The fact
is that there are more people in the world, more people wanting to
eat fish because it’s a high-quality source of protein, and
less fish in the oceans to feed them. Aquaculture is working with
commercial fishing to fill the gap between supply and demand with
fish.
Commercial fishing is an important industry for American workers.
It provides jobs for fishermen as well as ice suppliers, processing
plants, and local merchants.9 Many communities survive because of
the fishing industry, and are struggling with current stricter regulations.10 Aquaculturists are taking advantage of the infrastructure that is
already in place for commercial fishing to market their fish. This
means that jobs are created in areas that are dependent on fishing
for income.11Both fishing and aquaculture have their own environmental
concerns, which must be taken into account. Commercial fishing has
developed over the years to be extremely efficient in its ability
to catch a large amount of fish in a small amount of time. Unfortunately,
one of the side effects of this efficiency is bycatch. Bycatch is
when fishermen catch fish other than their target species. Because
of the way licenses are issued, these extra fish must be thrown back,
which puts stress on the fish population.12
One great advantage of aquaculture is its ability to breed fish
that are ideal for the market, thereby ensuring demand. Fish from
farms can also be fresher and available year round.13 But if these
selectively bred fish escape, they can breed with fish in the wild
and threaten the natural biodiversity found in species.14 Fish
feed from farms can also threaten ecosystems if it is present in
excess, or if it contains antibiotics.12
As aquaculture grows and expands to new areas of the world, it
will have to depend on the knowledge of local fishermen. Fishermen
have in depth knowledge of local fish, weather, and migration
patterns. With the help of fishermen, aquaculturists can set
up farms where they will not interfere with local fish and fishermen.
Off-shore fish farms may also be able to get assistance from
fishermen harvesting catch on their vessels.
If aquaculture and commercial fishing work together, the advantages
from each will help to create a self-sustaining, efficient seafood
market in America. The high-density fish farms will be able to
supply more fish to the American market, alleviating the need to
import seafood.13 Since these farms are not dependent on wild populations,
the stress that is currently put on them can be alleviated, and
eventually the ecosystems will be healthy again.
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Is
it safe to eat Farmed Fish?
Fish have been farm rasied for centuries to provide protein in
places where it was hard to get. A healthy diet should include a
variety of protein sources. There are many benfits to including fish
in your diet:
- Fish contain
Omega-3 fatty acids, which may help reduce the risk of heart
disease and cancer, lower blood pressure, reduce depression,
and relieve the pain of rheumatoid arthritis.15
- Omega-3
fatty acids are essential to brain, nerve, and eye development,
and may help reduce the symptoms of ADHD and the risk of
asthma.16
Recently,
there have been concerns about how safe it is to eat farm-raised
fish. Limited research has found that some farmed raised
fish contained harmful chemicals called polychlorinate biphenyls
(PCBs).15 However, there are safeguards implemented by the government
to insure that the food we consume is safe for us:
- FDA regulations
limit the amount of PCBs in seafood to 2,000 parts per billion,
which is 100 times larger than the amount of
contaminants found in the recent studies.15
- EPA
guidelines say that fish containing levels of PCBs between 24
and 48 parts per billion should be limited to 8 ounces a month,
which is approximately
3 servings.15
- EPA regulations
are based on eating fish from one contained source, which would
increase the likelihood of consuming too much
of a single contaminant.15 Generally, eating protein from a variety
of sources is healthier.
These regulations exist because it is known that wild fish can
be contaminated with heavy metals, such as mercury, as well as
PCBs, dioxins and other pollutants that they absorb from their
food.16 The levels of PCB contaminant found in wild and farm-raised
fish are similar.17 However, work is underway in the aquaculture
industry to reduce the source of contamination in fish feed, which
would eventually make farm-raised fish healthier than wild fish.18
The contamination levels that the FDA allows in marketed fish
are low enough that you can eat two meals of fish per week without
worrying about health risks.19 You can also eat more than two fish
meals per week if this is not done regularly.19 With the advance
of current aquaculture research, the number of servings recommended
per week will increase, making it easier to gain the health benefits
available from fish.18
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Building
your own recirculating hatchery
Aquaculture is an excellent tool to be used in an educational
setting. Several subjects can be incorporated into aquaculture:
history, English, math, biology, chemistry, economics and engineering.
A real life recirculating system that mimics a production scale
system can be used an exciting tool to demonstrate a growing industry
in a classroom or school. It is self-contained, requires minimal
maintenance, and user friendly to teachers and students. One could
set up a fish tank and use that to teach many of the same subjects
of study, but by using a real life model of a industrial system,
students will be able to identify with the process of building
a functioning system out of several different types of materials
and tools.
References:
1
http://www7.taosnet.com/platinum/data/light/whatis/history.html
2 http://www.cyfernet.org/curricul/aquacul.html
3 http://ag.arizona.edu/azaqua/extension/Classroom/overview.htm
4 http://www.dnr.state.sc.us/marine/mrri/shellfish/clam.htm
5 http://www.csa.com/hottopics/aquacult/oview.html
6 http://www.fao.org/docrep/003/w7499e/w7499e14.htm
7 http://www.oceansatlas.org/servlet/CDSServlet?status=ND0xODA0OCY3PWVuJjYxPSomNjU9a29z
8 http://ressources.ciheam.org/om/pdf/c55/01600222.pdf
9 http://www.theissue.com.au/www_root/pdf/ti0202fe.pdf
10 http://eesc.orst.edu/salmon/human/commfish.html
11 http://seagrant.gso.uri.edu/noreaster/noreasterFW97/aquaculture.html
12 http://www.pisces.demon.co.uk/factshe6.html
13 http://seagrant.gso.uri.edu/noreaster/noreasterFW97/aquaculture.html
14 http://eesc.orst.edu/salmon/human/hatcheries.html
15 http://www.salmonfarmers.org/nutrition/safety.html
16 http://www.newmediaexplorer.org/chris/2004/01/10/farmraised_salmonpcb_levels_higher.htm
17 http://www.salmonfarmers.org/media/01_08_04.htm
18 http://www.salmonfarmers.org/media/01_09_04_b.htm
19 http://www.fda.gov/fdac/features/2004/304_fish.html
Related
links:
Fish
Life Cycle
Species
raised at the Finfish Hatchery
Table
Top Recirculating System
Facilities
overview
The
MIT FinFish Hatchery
MIT Sea Grant's Aquaculture Curriculum On-line
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