Marine Aquaculture
Marine aquaculture or mariculture is the
cultivation of marine life for human consumption or
use-farming and gardening of the sea. Although the most
common purpose of mariculture is to produce marketable
food, there are other possible uses: e.g. to strip sewage
water of its toxic contaminants and nutrients, to produce
substances for food processing or industrial use, and to
produce medicines and medical products.
- Aquaculture in coastal waters is becoming more common
throughout the world. Because of unsustainable practices
and poor coastal management, aquaculture has exceeded
environmental limits in some regions. There is a great
potential for "sustainable" aquaculture that does not
damage and may even enhance coastal ecosystems, but it
has not yet been realized.
- Industrial scale and congested aquaculture facilities
often create pollution leading to severe habitat
destruction, The pollution comes from feces and food
wastes flushed into the surrounding environment,
- The siting of culture facilities often does not take
into consideration their interaction with the surrounding
environment. They are often placed in inappropriate
locations where environmental damage and/or aesthetic
problems are maximized.
- Marine aquaculture often has resulted in the
introduction of non-native species. Sometimes such
species are purposely released into the local environment
to grow, reproduce, and be harvested as has been done
along the west coast of the U.S. with the non-native
Japanese oyster and Manila clam. Other species escape
from more confined culture facilities. Some species
associated with imported aquaculture species are
unknowingly introduced. For example, the oyster drill, a
species of anemone, and Spartina marsh grass were all
accidentally transferred into Pacific coast waters with
oysters imported for aquaculture.
- The use of hatcheries to augment wild populations of
popular fisheries species may in the end interfere with
those wild populations by interbreeding with them and
thereby altering their genetics and survival rates.
- Aquaculture might also endanger native sealife by
exposing it to diseases that run rampant in the
overcrowded and stressful conditions of aquaculture
facilities. The use of antibiotics to reduce diseases in
the culture systems only adds to the potential
environmental problems in natural waters. The full
effects of antibiotics on native sealife are as yet
unknown.
- Some coastal aquaculture practices permanency alter
natural habitats. For example, shrimp ponds are often
constructed by cutting down mangrove habitats along
tropical coastlines. This activity has been responsible
for the loss of two-thirds of mangrove forests in the
Philippines, more than half in Thailand, and more than a
fourth in Ecuador.
- Aquaculture often uses feed derived from fish caught
specifically for fish-meal production. Using wild fish to
grow farmed fish defeats dhe whole purpose of "feeding
the world" more efficiently with aquaculture. There is,
however, a concerted research effort to develop vegetable
protein feeds that are efficently utilized.
- While there are attempts by the aquaculture industry
to retrofit some of their technologies to make them
individually more sustainable and compatible with the
ecosystem, there has been no concerted government or
industry effort to evaluate or manage aquaculture to make
it regionally sustainable or to integrate it into the
ecology and sustainable management of the coastal
zone.
- Although aquaculture is often considered an important
contribution to feeding growing human populations, marine
aquaculture focuses upon luxury markets which maximize
profits.
- Marine aquaculture is often touted as a replacement
for fisheries lost to overfishing, but in many cases it
may, in fact, negatively impact wild fish populations.
For example, in New England money is being requested for
developing the aquaculture industry without always
considering the impact on the local habitats upon which
the recovery of wild fisheries depends.
- There is a tendency to over-develop a single type of
coastal aquaculture in a region-e.g. salmon in western
North America, shrimp in certain tropical countries. The
intensive cultivation of a single species over a large
area has been shown to compound environmental problems,
whereas an appropriate mixture of species can minimize
environmental problems.
- Regulations on coastal aquaculture are often
ill-conceived and may present unnecessary difficulties
for the aquaculture industry as well as fail to protect
the environment.
- Innovative aquaculture has not been well supported,
so ecologically sound alternatives to destructive
aquaculture are not fully developed or readily available
on a commercial scale.
- In the U.S., several kinds of shellfish are
cultivated, usually in estuary settings. Oysters,
mussels, clams and other molluscs are the most common,
and some shrimp mariculture occurs on the Gulf coast.
With shrimp stealing the limelight because of the
environmental havoc their culture has wrought world wide,
not enough attention has been given to the other
shellfish that can be grown sustainably.
- Marine finfish aquaculture has been less common,
except for hatcheries which are commonly operated to
enhance stocks of wild fisheries. But now salmon are
widely cultivated and a few other fish are being
developed, in particular the red drum, which grows on the
Gulf coast. Salmon are reared extensively in the
northwest, with the concomitant environmental
controversy, and are becoming more common in the
northeast, where the jury on environmental impacts is
still out.
- The potential for marine aquaculture to provide a
variety of foods and services while maintaining healthy
ecosystems has been the subject of many research projects
and academic conferences. Research on sustainable matine
aquaculture often incorporates "polyculture" systems, in
which several different species are grown in the same
system-some marketable, some providing a service, such as
cleaning the water.
- The use of aquaculture in protecting or restoring
coastal ecosystems has been rare but shows promise, e.g.,
to restore saltmarsh plants and seagrasses and to
establish wetlands for filtering sewage water.
Goldburg, R. and T. Triplet. 1997. Murky Waters:
Environmental Effects of Aquaculture in the US.
Environmental Defense Fund. New York, NY.
National Research Council. 1992. Marine Aquaculture
Opportunities for Growth . National Academy Press.
Washington, DC.
Pacific Congress on Marine Science and Technology. 1995. Proceeding of the PAGON Conference on Sustainable
Aquaculture '95. Honolulu.
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