13 February 2021 | New Scientist | 39consumed directly by humans, and is projected
to increase as demand for seafood rises but the
catch from the wild stays essentially flat.
Aquaculture is the fastest-growing sector
of global food production. The vast majority
happens in Asia, largely for local consumption.
Western consumers mostly encounter it in the
form of farmed salmon or shrimp. For those
consumers striving to make ethical choices,
that can spell trouble.Trouble on the farm
Fish farming has some well-known and
undeniable problems, says Grant Stentiford
at the Centre for Environment, Fisheries
and Aquaculture Science in Weymouth, UK.
Farmed shrimp, for example, mostly comes
from southern and South-East Asia and
Ecuador, reared in ponds that were created
by destroying mangrove swamps. “There
has been a loss of habitat and biodiversity
in relation to those industries. I don’t think
anyone can really argue about that,” says
Stentiford. Add in the environmental cost
of feeding the shrimp and freighting them
to Western markets, and their calorie-for-
calorie carbon footprint can sometimes
exceed that of beef.
Salmon farming, meanwhile, has
well-publicised problems with parasites,
the overuse of antibiotics, escaped fish
breeding with wild ones – potentially diluting
the gene pool of wild fish and in some cases
leading to sterile offspring – and pollution of
the sea floor underneath the pens. Producers
are aware of these problems and are trying to
clean up their act, says Stentiford, but there is
a long way to go.
Aquaculture is also considered in the Aichi
targets, which say that by 2020 it should be
“managed sustainably, ensuring conservation
of biodiversity”. Unsurprisingly, the target
wasn’t met. Although most artisanal
freshwater aquaculture is sustainable, sea-
based aquaculture – called mariculture – isn’t.
According to the latest assessment of these
targets, it is responsible for “large-scale loss
and destruction of coastal wetlands (especially
mangroves), and pollution of soil and water”.
Another huge problem with aquaculture
is that, paradoxically, it often increases the
pressure on wild fisheries. Salmon, tuna, sea
bass and many other farmed species are top
predators that eat other fish. To meet this
demand, around 22 million tonnes of wild >instance. Then industrial fishing quadrupled
the catch, collapsing the stock in 1992. It has
since recovered somewhat, and now produces
around 20,000 tonnes a year – a number that is
considered “sustainable”, says Pauly.
“A better question to ask is, how much of
the biomass that you had in the water in 1950
is left,” he says. By that measure, nearly all
of the world’s fish stocks are profoundly
depleted. “If you look at big fish, the biomass
has diminished enormously, on the order of
80 to 90 per cent.”
Sustainability also often fails to take
into account wider ecological factors. The
langoustine fishery in the Firth of Forth in
Scotland, for example, is sustainable, but only
because so many other species have been
fished to extinction and the langoustines no
longer have any natural predators, says Pauly.
You also have to consider that fishing vessels
are more powerful than they once were, says
Pauly. “Even though the biomass has declined,
they are able to compensate by finding the few
fish that remain, and being able to operate
where old trawlers would not be able to,” he
says. “The fact that our trawlers maintain
catches is not an indication that abundance
has remained the same.”
If that wasn’t bad enough, there is also
the greenhouse gas emissions of wild fishing
operations to consider. According to a recent
assessment, per kilocalorie of food produced,
wild-caught fish has a bigger global warming
footprint than pork, chicken or dairy (see
“Carbon costs of food”, page 40). Trawler
NOTE: EXCLUDES AQUATIC MAMMALS, CROCODILES, ALLIGATORS AND CAIMANS, SEAWEEDS AND OTHER AQUATIC PLANTSMillion^tonnesYe a r0204060800020406080950 960 970 980 990 2000 20 0 20 8Aquaculture
Wild-caught fisheriesGlobal demand for fish keeps rising
Aquaculture is rapidly expanding to satisfy the world’s appetite for seafoodfisheries are the worst, but that is even the
case for the lowest-impact wild fisheries. It is
because of the huge amount of fuel needed
to power long-distance travel over weeks or
months, to haul heavy fishing gear, as well as
the energy costs of cooling or freezing the fish.
Overall, it is obvious that wild-caught fish
come with some hard-to-swallow side orders.
“The story of our treatment of the oceans is a
shameful one and a very frightening one,” says
Tara Garnett at the University of Oxford’s Food
Climate Research Network.
Maybe, then, the answer is aquaculture, aka
fish farming. This large and rapidly growing
sector already supplies 52 per cent of the fishBottom trawler fishing disrupts
seabed habitats. It is also very
carbon intensiveFR
ED
RIKNAUMANN/PANOS