Environmental Engineering Reference
In-Depth Information
marine invertebrates. Catch reconstructions for various maritime nations showed
that the ofi cial statistics underestimate their likely true catch—that is, reported
landings plus illegal, unreported, and unregulated (IUU) catches—by as much as a
factor of two or more (Zeller and Pauly 2007). And these discrepancies were found
not only for low-income countries but even for Greece, a member of the EU: Tsikli-
ras, Moutopoulos, and Stergiou (2007) found that between 1964 and 2003, the
FAO data underestimated actual landings by an average of 35%, with an error range
of 10%-65%.
The single most important reason to question recent global FAO landings data
during the last decades of the twentieth century was the massive overreporting of
Chinese i sh and invertebrate landings. Watson, Pang, and Pauly (2001) showed that
while the ofi cial reports of Chinese marine catches kept on rising between the mid-
1980s and 1998, other evidence pointed to declines averaging 360,000 t/year; as a
result, the total 1998 catch in China's exclusive economic zone and in distant waters
was not 15 Mt but perhaps as little as 5 Mt. The FAO had also acknowledged these
Chinese overestimates. At the same time, there has also been a great deal of illegal
i shing, and the FAO does not make any attempt to estimate it.
The i rst worldwide analysis of IUU catches concluded that their recent rate has
been between 11 and 26 Mt/year (Agnew et al. 2009). On the regional level, West
African waters (the eastern Central Atlantic) have had the highest level of illegal
i shing, amounting to nearly 40% of the reported catch, and areas with illegal i shing
rates above 30% of the acknowledged landings are the western Central Pacii c
(34%), the Northwest Pacii c (33%), the Southwest Atlantic, and the eastern Indian
Ocean (both 32%). In specii c term, the highest illegal catches are for demersal
i shes, salmons, trouts, and smelts (mostly over 40%), the lowest (less than 10%)
for l ounders, halibuts, and soles.
Ofi cially tabulated landings also exclude discarded by-catch, the zoomass of all
unwanted species caught alongside the targeted catch, including i sh and inverte-
brates, marine mammals (most often dolphins), reptiles (most often turtles enmeshed
in i shing nets), and even seabirds, including gannets, fulmars, pufi ns, albatrosses,
and petrels killed by tuna drift nets and longline i sheries (Gales, Brothers, and Reid
1998; Rogan and Mackey 2007). But it also includes desirable commercial species
that are smaller than the allowable size or are over the permissible catch quota, and
females that are protected for breeding. By-catch is simply discarded overboard,
and both its share in specii c i sheries and the survival rates of discarded species
vary widely. Discards can amount to a small fraction of actual landings or (as in
tropical shrimp trawling) can be an order of magnitude greater than the catch itself.
