Around the world, people are eating more
seafood than ever before. Demand is increasing due to
growing populations, and because health-conscious consumers
are choosing seafood more often. To help supply the
global demand for seafood, people are raising fish,
shrimp and oysters like farmers raise cattle and chickens.
Today, almost 20% of our seafood comes from farms. The
ecological impact of fish farming depends on which species
are raised, how they are raised and where the farm is
Fish farms depend on wild fish
While farmed fish and shellfish can supplement our seafood
supply, they can't replace the variety and abundance
of seafood from the wild. Most seafood farms depend
on healthy wild populations to supply eggs or young
that the farmers raise for market. Many fish farms also
depend on wild fish, like anchovies, as food for the
Farmed shellfish are a Best Choice Most oysters
on the U.S. market, and many of the clams and mussels,
are farm-raised. These shellfish filter tiny plankton
out of the water for their food, so they need no supplemental
feeding. Shellfish can even improve water quality as
they clear the water of excess plankton. And because
shellfish for human consumption must come from clean
water, shellfish farming often spurs efforts to keep
coastal waters clean.
Clams are raised in special beds on sandy shores, where
their harvest does little to disturb the ecosystem.
Oysters and mussels are often raised in bags or cages
suspended off the seafloor, doing little damage as they're
Net-pen farming can be a messy business
Many farmed fish, including most farmed salmon, are
raised in net pens, like cattle in a feed lot. Thousands
of fish concentrated in one area produce tons of feces,
polluting the water. Diseases can spread from fish in
the crowded pens to wild fish. Antibiotics and other
drugs used to control those diseases leak out into the
environment, creating drug-resistant disease organisms.
And if farmed fish escape their pens, they can take
over habitat from wild fish in the area. While the U.S.
has laws to protect the environment around coastal fish
farms, many nations that supply farmed fish to U.S.
markets do not.
Shrimp farming can harm the coast
In Thailand, Ecuador and many other tropical nations,
coastal forests of mangroves once sheltered wild fish
and shrimp, which local people caught to feed their
families. Mangroves also filter water and protect the
coast against storm waves. Many mangrove forests have
been cut down and replaced with shrimp farms that supply
shrimp to Europe, Japan and America. After a few years,
waste products build up in the farm ponds and the farmers
have to move on. The local people are left with no shrimp
farms—and no mangrove forest.
Far from the sea may be best
The best way to raise fish may be inland, far from
coastal waters where wild fish feed and breed. Tilapia,
a plant-eating fish, is easy to raise, and produces
protein for people without using wild fish as feed.
Catfish and trout are raised inland in the United States.
All of these fish can be delicious alternatives to ocean-farmed
shrimp and salmon. Even shrimp and salmon farming can
be moved inland, where wastes are easier to handle.
U.S. shrimp farmers are experimenting with enclosed,
recirculating systems that filter wastewater and can
be located far from the coast.
Information courtesy of Monterey Bay Aquarium. Visit
their site. www.montereybayaquarium.org