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Aquaculture, freshwater andmarine 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. At present, marine capture fisheries yield 110–130
million tonnes of seafood annually. Of this, 70 million tonnes
are directly consumed by humans, 30 million tonnes are dis-
carded and 30 million tonnes converted to fishmeal.
The world’s fisheries have steadily declined since the 1980s, its
magnitude masked by the expansion of fishing into deeper and
more offshore waters (Figure 10) (UNEP, 2008). Over half of
the world’s catches are caught in less than 7% of the oceans, in
areas characterized by an increasing amount of habitat damage
from bottom trawling, pollution and dead zones, invasive spe-
cies infestations and vulnerability to climate change (UNEP,
2008). Eutrophication from excessive inputs of phosphorous
and nitrogen through sewage and agricultural run-off is a
major threat to both freshwater and coastal marine fisheries
(Anderson
et al
., 2008; UNEP, 2008). Areas of the coasts that
are periodically starved of oxygen, so-called ‘dead zones’, often
coincide with both high agricultural run-off (Anderson
et al
.,
2008) and the primary fishing grounds for commercial and ar-
tisanal fisheries. Eutrophication combined with unsustainable
fishing leads to the loss or depletion of these food resources, as
occurs in the Gulf of Mexico, coastal China, the Pacific North-
west and many parts of the Atlantic, to mention a few.
FOOD FROM FISHERIES AND AQUACULTURE