268
equal to the volume replenished
through reproduction. This is
usually achieved through quotas,
which limit the number of fish that
can be brought in during a season.
Quotas can curb unsustainable
fishing: for example, 16 percent of
fish stocks in American waters
were overfished in 2015, down from
25 percent in 2000. However, the
quota system can encourage
fishermen to take the largest fish
possible, and to throw back smaller
fish, which frequently die from the
stress of being caught. In many
cases, quotas are also not set at a
truly sustainable limit; commercial
fishermen often have considerable
lobbying power, and focus on theOVERFISHING AND THE GLOBAL MARINE FISHERIES CRISIS
short-term economic gains of
catching more fish rather than on
long-term sustainability. Fishery
management can be further
complicated by factors such as the
open access nature of the ocean,
illegal fishing, and an absence of
regulation and oversight.A worldwide crisis
Overfishing is now a global issue,
with more than 30 percent of the
world’s fisheries harvested beyond
their biological limits, and 90
percent of fish stocks currently
at their limits or overfished.
Sustainable management is now
essential if fisheries are to continue
to provide jobs and meet consumerdemand.
The management strategies
adopted depend on the nature of
the problem. If fish are being taken
before they are mature, this will
limit the stock’s future ability to
reproduce at a maximum level and
keep their numbers replenished.
Placing minimum size limits on
fish can help control this type of
overfishing. If too many mature fish
are being caught, this could leave
too few to reproduce and replenish
the present population. In this case,
moratoriums and quotas are among
measures that can help. Finally,
ecosystem overfishing occurs when
a fishery is so depleted that the
ecosystem itself changes and is
no longer able to support the fish
stock at a sustainable level. It
generally occurs when large
predatory fish are overfished,
allowing populations of smaller
forage fish to increase and alter the
entire ecosystem. This happened
in the North Atlantic cod fishery:
without the cod to keep them in
check, the cod’s three main food
sources—shrimp, crab and capelin
fish—all increased in numbers.
The overfishing problem is now
compounded by climate change
and pollution, which are also
affecting ocean ecosystems. The
consequences could be dire. IfAltered ecosystem structure and function
Physical impact
of fishing gearBycatchIncidental
mortalityDecline (^) in m
ean trophic level
Large-scale fishing
operations disturb the balance
of marine ecosystems in
various ways, depleting the
target fish species, upsetting
the food chain, and damaging
the marine environment.
Disrupting the ecosystem
Discarded
bycatch
and offal
Harvest
mortality
Habitat
modification
or destruction
Biological
interactions
I didn’t take
the fish from the
goddamn water.
John Crosbie
US_266-269_Overfishing.indd 268 12/11/18 6:25 PM