Fish farming – can it help feed the world without destroying the environment?
by Tresa Erickson |
Fish farming, or aquaculture as it is otherwise known, has been
around for centuries and has become a lucrative practice worldwide. The
National Oceanographic and Atmospheric Agency estimates the industry to
be worth $40 billion. With urban expansion taking up more and more
farmland, many believe fish farming is one of the solutions to feeding
the world’s six billion people. However, while it has contributed to
the world’s food supply, fish farming has also taken its toll on the
environment.
Although it has helped restore some fishery stocks, such as the
oyster stock in Chesapeake Bay, fish farming has led to a reduction in
other stocks. The problem begins on farms that raise carnivorous fish,
like marine shrimp, salmon, trout and bass. To raise one pound of
carnivorous fish, it takes almost three pounds of feed. Unfortunately,
the feed is made from smaller wild fish, including herring, mackerel,
anchovies and sardines. Of the 29 million tons of carnivorous fish
raised in 1997, 10 million tons of wild fish were used in the feed.
Another 22 million tons were used in pig and cow feed.
If this rate of harvest continues, some stocks of wild fish will be
significantly reduced, while others may disappear altogether. The
world’s population will suffer, as will the other species that feed on
the wild fish to survive. To combat the problem, researchers are
looking into alternative feeds that contain the amino acids carnivorous
fish need to survive, but it will take some time before the feeds are
put on the market.
While some farmers choose to raise carnivorous fish, others raise
fish that feed mostly on plants. Some of these omnivores include carp,
catfish, tilapia, milkfish, scallops and oysters. Because their diet
consists mostly of plants, they require very little feed and do little
damage to wild fish stocks. However, as land becomes scarce, farmers
will dip into wild fish stocks more in an attempt to grow larger fish.
To beef up the omnivores, farmers will add more feed to their lakes and
streams, leading to a significant reduction in wild fish stocks. The
trend has already started in Asia where farmers produce more than 10
million tons of carp and tilapia annually on very little land.
In addition to reducing wild fish stocks, fish farming may also lead
to the destruction of natural habitats. In Asia, for example, thousands
of acres of mangrove forests and coastal wetlands have been converted
into milkfish and shrimp ponds. As a result, many native species,
including some shellfish, have lost their natural habitat.
When farmed fish escape into the wild, they can wreak even more
havoc on the native species. In the Atlantic Ocean, for example, farmed
salmon compete with native salmon on a daily basis. Nearly 40 percent
of those caught originated on a farm. According to researchers,
farm-raised salmon have bred with native salmon, altering their genetic
makeup, which could ultimately lead to their extinction. Farmed fish
that have escaped may also be responsible for the spread of diseases,
like the Whitespot and Yellowhead viruses, which have wiped out many
shrimp farms in Asia.
Fish farming isn’t all bad. As noted earlier, it does contribute to
the world’s food supply, and when carried out properly, it can help
restore stocks. However, to benefit fully from it, fish farmers must
take the appropriate measures to raise a productive crop without
harming the environment.
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