Jose Cort/Courtesy NOAA11
The Ocean and Fisheries
DEPLETING BLUEFIN TUNA STOCKSS
tocks of the giant, or Atlantic, bluefin tuna, highly
prized for sushi, are classified as depleted in the
Mediterranean Sea by the U.N. Food and Agriculture
Organization. Once harvested sustainably through
traditional trapping, Mediterranean bluefins are now
fished—often illegally—at approximately four times
the sustainable rate. Spotter aircraft locate fish stocks
and alert huge fishing fleets, whose ships (see inset
photograh) cast purse seines, which envelop schools of
fish and cinch to close around them. Captured bluefins
are fattened in offshore pens (see large photograph)
before being butchered for market. The enormous
economic value of the huge bluefin places it at great
risk. Only recently have Mediterranean nations begun
implementing conservation measures to protect the
species, including a ban on the purse seine harvest
of bluefins in Mediterranean and east Atlantic waters.
But although the International Commission for the
Conservation of Atlantic Tunas (ICCAT) places yearly
catch limits—quotas—on the fishery, illegal harvests
result in the total trade exceeding these quotas by
approximately 30 percent (see graph). At these catch
rates, ICCAT estimates that the Mediterranean bluefin
stocks have less than a 24 percent chance of rebuilding
by 2022. Conservation efforts have accelerated,
however: In late 2011, ICCAT agreed to implement
electronic documentation of catches, to help eliminate
illegal trade.
Overfishing, the harvesting of fishes faster than
they can reproduce, is not limited to the Mediterranean.
Worldwide, more than 80 percent of fish species have
been overfished, with some U.S. commercial fish stocks
depleted by as much as 95 percent, as demand for fish
has grown and harvesting methods have become more
sophisticated. Ecologists and economists estimate
that if overfishing and ocean pollution aren’t curbed,
populations of virtually all harvested seafood species
could collapse by 2048.