For 25 years fish farming has been touted as "the next great leap" in
food production. The World Bank and many others promised that rearing fish in ponds or
coastal-water "netpens" would yield cheap, high-quality protein while relieving
pressure on overfished wild populations. Aquaculture now accounts for a quarter of the
world's fish supply, and farms for freshwater species such as catfish and tilapia do
indeed seem to be sustainable.
The same cannot be said for two of aquaculture's most
rapidly expanding sectors, shrimp (see "The Hidden Life of Shrimp," July/August
1998) and salmon. "Salmon farming probably causes more problems per pound of fish
than any other form of aquaculture," says Jim Fulton, executive director of the David
Suzuki Foundation, a Canadian nonprofit that supports environmental education and
Salmon farming began in Norway in the 1960s and spread to North America in the 1980s
and Chile in the 1990s. The farms float open-topped netpens in coastal bays to raise
fingerlings to maturity. Most operations, even in the Pacific, raise Atlantic salmon
because they are adaptable, mature quickly, and spawn over a long time. Aquaculture
produces over 710,000 tons of salmon a year, roughly half the world's supply.
To "grow" one pound of carnivorous salmon, however, takes almost three pounds
of other fish, thus increasing fishing pressure. (In contrast, sustainably farmed
freshwater species are raised on a largely vegetarian diet.) Open-water salmon pens also
leak tons of feces and surplus food, polluting shoreline ecosystems; Norway's farms emit
as much nitrogen as would the untreated waste of 4 million people.
Worse, the millions of salmon that escape from netpens each year may be disrupting wild
salmon populations by introducing diseases and parasites, competing for habitat, and
interbreeding. On the West Coast, fugitive Atlantic salmon have been caught in waters from
the Pacific Northwest to the Bering Sea. Successful spawning by farm fugitives has been
confirmed in at least two cases in Alaska, suggesting that populations are infiltrating
the hundreds of streams that don't get closely studied. "Probably ninety-five percent
of our streams aren't accessible by road, so they're generally only monitored by airplane
surveys-and it's hard to spot a few Atlantic salmon from a plane," explains Glen
In 1990, Alaska banned not just salmon but virtually all aquaculture from state waters.
"What we've seen since then in British Columbia has only confirmed our doubts,"
says Brian Paust, a professor of fisheries at the University of Alaska in Fairbanks. Calls
for tougher regulations are also coming from Washington State, where 100,000 Atlantic
salmon escaped from their netpens into Puget Sound last June.
Even on the East Coast, escaped Atlantic salmon vie directly with their wild cousins.
Faster-maturing and more aggressive farm salmon may initially outcompete smaller, more
cautious wild fish, but ultimately fail to survive. Breeding escapees may also alter the
genetic makeup of wild fish, robbing offspring of the instincts needed to migrate and
And last year, federal biologists captured dozens of wild Maine salmon that carried a
deadly virus detected only once before, 20 years ago in Scottish farm salmon. Some
biologists worry that the virus may have contributed to the decline of Maine's wild
Atlantics since then, despite improvements in their spawning habitat.
"Salmon farming as it's done now is simply unacceptable," says the Suzuki
Foundation's Fulton. "It needs a complete overhaul." Fulton and many other
environmentalists and wildlife managers call on the industry to abandon saltwater netpens
in favor of more costly land-based closed ponds or tanks.
What can you do? Lobby your legislators (particularly in Canada, Maine, and Washington
State) for industry reform, and buy only wild salmon. Other well-managed and abundant wild
species include striped bass, Pacific halibut, squid, and crabs (except Alaskan kings).
Among farmed varieties, try catfish, tilapia, or crawfish, or mollusks such as clams,
oysters, and mussels. The ocean's bounty can be safety harvested, but it takes caring
farmers and informed consumers.
David Dobbs, coauthor of The Northern Forest, writes on the environment from his
home in Montpelier, Vermont.