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At present capture fisheries yield 110–130 million tonnes of sea-
food annually. Of this, 70 million tonnes are directly consumed
by humans, 30 million tonnes are discarded and 30 million
tonnes converted to fishmeal. Aquaculture, freshwater and ma-
rine fisheries supply about 10% of world human calorie intake
– but this is likely to decline or at best stabilize in the future,
and might have already reached the maximum.
The primary and most important fishing grounds are found
along the continental shelves within less than 200 nautical
miles of the shores. The distribution of these fishing grounds
is patchy and very localized. Indeed, more than half of the 2004
marine landings were caught within 100 km of the coast in
depths generally less than 200 m covering an area of less than
7.5% of the world’s oceans, while 92% was caught in less than
half of the total ocean area.
Climate change and increased CO
2
assimilation in the oceans
will result in increasing ocean acidification, die-back of up to
80% of the world’s coral reefs and disruption of thermoha-
line circulation and other processes. It will particularly impact
dense-shelf water cascading, a “flushing” mechanism that
helps to clean polluted coastal waters and carry nutrients to
deeper areas. Coastal development is increasing rapidly and
is projected to impact 91% of all inhabited coasts by 2050 and
contribute to more than 80% of all marine pollution. Increased
development, coastal pollution and climate change impacts on
currents will accelerate the spreading of marine dead zones,
many in or around primary fishing grounds (Diaz and Rosen-
berg, 2008).
Overfishing and bottom trawling are reducing fish stocks and
degrading fish habitats, and threatening the entire productivity
of ocean biodiversity hotspots, making them more vulnerable
to climate change. Up to 80% of the world’s primary fisheries
stocks are exploited close to or beyond their optimum harvest
capacity and large areas of productive seabeds on some fishing
grounds have been partly or extensively damaged. For example,
over 95% of the damage and change to seamounts has been
caused by bottom trawling, which has been estimated to be
as damaging to the seabed as all other fishing gear combined.
Damaged from overfishing , bottom trawling and pollution, the
worlds fishing grounds are increasingly becoming infested by
IMPACTS OF ENVIRONMENTAL DEGRADATION ON FISHERIES
invasive species mainly through ballast water, with the pattern
closely following the major shipping routes.
The result of unsustainable fishing practices are that we might
no longer able to increase the landings from conventional
fisheries, and might, in fact, be facing a substantial decline
in the world’s fisheries in the coming decade. This will also
have severe impacts on aquaculture production, which relies
on fish for feed.
AQUACULTURE
Aquaculture production has increased more than seven-fold in
weight (from 5 to 36 million tonnes) between 1980 and 2000.
The value generated has grown from US$9 billion in 1984 to
US$52 billion in 2000 (Deutsch
et al
., 2007). In 2006, the world
consumed 110.4 million tonnes of fish, of which 51.7 million
tonnes originated from aquaculture. In order to meet the grow-
ing fish demand, aquaculture will have to produce an additional
28.8 million tonnes – 80.5 million tonnes overall – each year, just
to maintain per capita fish consumption at current levels. Aqua-
culture growth rate is declining, however: a yearly growth rate of
11.8% from 1985 to 1995 slowed to 7.1% during the following de-
cade, and to 6.1% for the 2004–2006 period. In October 2008,
FAO cautioned that a series of emerging challenges need to be
addressed if aquaculture is to meet increasing demand for fish.
THE FEED BOTTLENECK
Almost 40% of all aquaculture production is now directly de-
pendent on commercial feed. Most farmed fish that are con-
sumed in the developing world, such as carps and tilapia, are
herbivores or omnivores. But other species like salmon or
shrimp – often raised in developing countries – are fed other
fish in the form of fishmeal or oil. Salmon, shrimp and trout
aquaculture alone accounts for almost 50% of all fishmeal used
in aquaculture, but provides less than 10% of the production
volumes (Deutsch
et al
., 2007). In 2006, aquaculture con-
sumed 3.06 million tonnes (56%) of world fishmeal production
and 780,000 tonnes (87%) of total fish oil production. Over
50% of the sector’s use of fish oil occurs on salmon farms. Fish-
meal and fish oil production has remained stagnant over the
last decade and significant increases in their production are not