May 2022, ScientificAmerican.com 49human-generated feed or energy, a boon for the envi-
ronment as well as for his bottom line.
A far more controversial experiment in Maine in -
volves cultivating finfish such as salmon and yellowtail
either in immense net pens in the ocean or, more recently,
in land-based operations where thousands of metric tons
of fish circle gigantic tanks like felons pacing around a
prison yard. Fish in these recirculating aquaculture sys-
tems (RAS) consume a steady diet of scientifically
designed feed and, if need be, infection-fighting drugs.
The current they swim against is artificially generated,
as is the LED light that bathes them up to 24 hours a day
to hasten their growth. It is a surreal scenario, but pro-
ponents claim RAS are well positioned to bolster Maine’s
economy while serving the nation’s growing demand.
“The U.S. runs an enormous seafood deficit,” says micro-
biologist Deborah Bouchard, director of Maine’s Aqua-
culture Research Network, noting the country relies
heavily on fish imported from other nations. “Maine is
building on the opportunity to fill the gap.”
Oceanographer David Townsend, director of the
School of Marine Sciences at the University of Maine,
says the state has two important attributes for fish culti-
vation: cold, nutrient-rich water and extremely vigorous
tides that distribute those nutrients throughout the water
column. “Our coastal waters are very productive,” he says.
But the farming of large, carnivorous fish makes
some scientists uneasy. Recirculating tanks require
huge amounts of energy to move and filter millions of
gallons of water daily, and that water still holds waste
that can pollute nearby rivers and estuaries. Also,
there’s a matter of the fish and their welfare. “Farming
finfish on an industrial scale is like farming livestock
on land on an industrial scale,” says economist Rosa-
mond L. Naylor, who directs the Center on Food Secu-
rity and the Environment at Stanford University. “There
are ways to minimize risks, but they are costly, and not
everyone is taking the steps they should be taking.”
The question of whether industrial aquaculture will
enrich Maine’s economy without damaging its fragile
ecosystems haunts scientists, politicians and residents.
The Gulf of Maine is the least alkaline body of water on
the Atlantic coast between Mexico and Canada, and its
delicate chemistry is particularly vulnerable to disrup-
tions both natural and human caused. Whatever their
outcomes, Maine’s experiments will set an important
precedent for seafood production around the globe.S
cieNtists agree that the food supply must
increase substantially to feed the world’s growing
population and that cultivated fish, shellfish and
algae will play a major role in that expansion. Aquacul-
ture is already the world’s fastest-growing sector of food
production, churning out more than half of all fisheries
products, and seafood is the most traded commodity on
the planet. But although Americans eat a lot of seafood,
relatively little is homegrown: an estimated 65 to 85 per-
cent of fish bought for consumption in the U.S. is im -
ported, most of it from China. The U.S. does not export
much farmed fish, either, because it grows so little of it.
According to the most recent data, from 2019, the U.S.
produced 490,000 tons of farmed fish, barely a rounding
error compared with the roughly 49 million tons pro-
duced by China.
Maine’s Atlantic salmon could help the U.S. compete.
Often called the “king of fish,” salmon are sleek, shiny
and beautiful. They are also an extremely popular menu
item, ranking second only to shrimp as America’s favor-
ite seafood. The cold-water fish were once plentiful in
Maine, but dams, overfishing, parasites and pollution
all led to the closing of the state’s wild Atlantic salmon
fishery in 1948, and today it is illegal to catch or sell