Environmental Engineering Reference
In-Depth Information
than 8,000 right whales and perhaps only 2,300 blue whales (IWC 2010), totals
that represent perhaps less than 10% and around 1% of the respective prewhaling
populations.
In contrast to whaling, virtually no effective restrictions have been put on most
of the world's commercial i shing even as i shing capabilities and typical vessel sizes
had undergone a great expansion. The change began during the late nineteenth
century with the introduction of steam-powered vessels. Unlike their wind- and
tide-driven predecessors, whose operation was limited by those natural energy l ows,
the new vessels could use destructive trawls (nets dragged across the sea bottom,
i rst introduced in England during the fourteenth century) continuously and they
could also deploy much larger nets. Clear signs of the advancing depletion of i sh
stocks in the most heavily trawled seas were seen in a matter of decades.
The adoption of diesel engines (a superior prime mover compared to steam
engines) after World War I further increased the power and operating radius of
typical i shing vessels, and the effects of both these factors were multiplied again by
the post-World War II introduction of large factory ships with on-board processing
and refrigeration. At the same time, i shing vessels also became equipped with sonar
and began to deploy monstrous drift nets (some up to 50 km long). All of these
technical advances have made it easier to satisfy the rising demand for marine foods
and led to what Pauly (2009) labeled a threefold expansion: i rst, the areal extension
of long-distance commercial i shing to tropical oceans and then to the circum-
Antarctic waters; second, the depth expansion as longline l eets and trawlers reached
the demersal waters; and third, the concurrent taxonomic expansion as i sheries
began to target previously spurned and unfamiliar taxa. After four decades this far-
reaching, high-tech vacuuming of oceans had predictable results: most of the major
i shing areas have become overexploited.
Signs of this trend have included the extension of i sheries well beyond the tra-
ditionally exploited waters, the capture of previously ignored, lower-value species,
and rising prices. The widening range of operation is best illustrated by the history
of Japanese i shing. During the occupation period it was restricted to only about
40% of the area in the eastern Pacii c that it accessed before the war, but by 1960
Japan's i shing activities had extended to the Pacii c and Indian Ocean waters sur-
rounding Australia, to the Central Atlantic, and to the extreme latitudes of the
Pacii c: the Bering Sea in the north and east of New Zealand in the south (Swartz
2000).
Perhaps the best example of a massive exploitation of formerly ignored stocks is
the i shing for Alaska pollock (
Theragra chalcogramma
), whose abundance attracted
