weight = 0.4, dry weight/wet weight = 0.3), we have:(^) And, finally, this must be converted to millions of metric tonnes (Mt):
(^) That is about double the global catch, including discarded bycatch. It is of importance that the world
fishery take is of the same order of magnitude as this outcome, whatever its associated uncertainty. It
definitely implies that removal of biomass by us, “the people”, is a very large factor in marine
ecology at higher trophic levels.
(^) If you examine the equation, you will see that it is exquisitely sensitive to the value chosen for EE, a
value we must guess. Putting potential catch at current catch, about 125 Mt, and solving for EE
(iteratively or by logs), gives 17%, by no means an unlikely mean value for the oceans, given the
state of current knowledge of trophic ecology. Of course, the calculation is also sensitive to the
trophic level chosen as representative for fishery production, the proportions assigned to coastal and
oceanic production, and the accuracy of the grand sum of primary production. You should explore
this yourself.
(^) If limitation of potential catch to one-third of production is eliminated, and EE is reduced to 10%, the
supposed potential is only 19 Mt, less than 20% of actual. This all but proves that EE around 10%,
which was assumed by ecologists a generation ago as standard, and which is still taught in elementary
ecology courses, must be too low for at least the oceans.
(^) We may very well be fishing accessible resources as intensely as the stocks can bear, or more
intensely in the long term, even if the apparent potential catch is double the actual catch. Accessibility
is the issue. Unexploited squid and krill alone represent enough productivity to account for the
difference. Other production at the trophic levels of fishery stocks appears in little-exploited jellyfish,
in mid-water fishes, and in widespread oceanic stocks not possible to exploit commercially. Thus, the
calculation, along with the recently flat catch totals and other considerations, suggests that we are
pushing close to the oceans’ potential to produce fish for human use.
Then in the mid-1980s came a series of recurring increases. The trawling industry
remained in place and output held steady for a time. Initially, the burst of the mid-
1980s was in the top few species: Alaskan pollock, Japanese sardine, capelin, and
Chilean jack mackerel. Several of these species, particularly the clupeids, had
dramatic increases after the Pacific regime shift of 1976. It was warmer, and
production was definitely greater in these stocks. Some fisheries responded
immediately (Japan, Chile), while others (herring off New England, the California
sardine) did not have the markets to drive a return to intensive harvests. Chilean
fisheries took much of the mid-1980s increase, and Chile was the No. 4, even No. 3,
fishing nation in those years. That was from fishing on sardine and mackerel stocks,
plus fishing along its southern coast on a variety of species. In the 1990s, the Peruvian
anchoveta fishery returned to over 9 Mt yr−1, in 1995 12 Mt, which covered some
declines in demersal stock production worldwide, actually raising the world total and
leading to 1996–1997 marine-capture fishery totals over 86 Mt. Those were the
highest totals to date. Total yield dipped in 1998 to about 78 Mt as the Peruvians
established a partial fishing moratorium during an El Niño. Anchoveta catches