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Figure 6. The World’s most productive fishing grounds are confined to major hotspots, less than 10% of the World oceans.
The maps shows annual catch (tonnes per km
2
) for the World’s oceans. Notice the strong geographic concurrence of con-
tinental shelves, upwelling and primary productivity (see Figures 4 and 5) and the amount of fish caught by fisheries.
(Johnston and Santillo, 2004; Morato
et al
., 2006b). Once deplet-
ed and devastated, often for decades to centuries, fishermen move
on to the next seamount to start the next cycle. However, with
many known seamounts already (over)exploited, recovery of fish
stocks on seamounts varies with each species. Stocks of orange
rough on the Chatham Rise in New Zealand, for example, show
possible improvements after 5 years, whereas the grenadier stocks
in the Northwest Atlantic show no signs after a number of years
of reduced quotas.
The depletion of seamount populations indicates that the current
focus and levels of fishing on seamounts is not sustainable. More
depletion, extirpations, and even species extinctions may follow if
fishing on seamounts is not reduced (Morato
et al
., 2006). Very
common however, rather than fishing until near extinction, is that
the fishing vessels will move on to the next location as soon as the
first is exhausted. With the large capacity of the fleet, the result is
that more and more locations become impacted and damaged.
When primary production and bathymetric maps (showing the dis-
tribution of continental shelves) are compared to the intensity of
fisheries (catch), a clear pattern erupts, reflecting the productivity
and accessibility of these ocean hotspots.