Page 460 - Environment: The Science Behind the Stories

Throughout the world’s oceans, today’s industrialized Many scientists conclude that most marine communities may
fishing fleets are depleting marine populations with aston- have been very different prior to industrial fishing.
ishing speed. In a 2003 study, Canadian fisheries biologists
Ransom Myers and Boris Worm analyzed data from FAO Several factors mask declines
archives and found the same pattern for region after region:
In just a decade after the arrival of industrialized fishing, catch Although industrialized fishing has depleted fish stocks in
rates dropped precipitously, with 90% of large-bodied fish and region after region, the overall global catch has remained
sharks eliminated. Populations then stabilized at 10% of their roughly stable for two decades (see Figure 16.19). This seem-
former levels. This means, Myers and Worm concluded, that ing stability can be explained by several factors that mask
the oceans today contain only one-tenth of the large-bodied population declines. Fishing fleets are now traveling longer
animals they once did. distances to reach less-fished portions of the ocean. They also
As we have seen (pp. 101–102), when animals at high are fishing in deeper waters; average depth of catches was
trophic levels are removed from a food web, the prolifera- 150 m (495 ft) in 1970 and 250 m (820 ft) in 2000. Moreover,
tion of their prey can alter the nature of the entire community. fleets are spending more time fishing and are setting out more

900 Advent of industrial
800
Cod harvested (thousands of tons) 600 trawling Moratorium
700

500
400
imposed
300
(1992)
200
100
0
1860 1880 1900 1920 1940 1960 1980 2000
Year
(a) Cod harvested from Grand Banks

60
Cod harvested (thousands of metric tons) 40 Advent of industrial Closures
50

enacted
(1994)
trawling
30

20

10

0
1900 1920 1940 1960 1980 2000 CHAPTER 16 • M AR in E A nd Co A s TA l s ys TEM s A nd R E sou R CE s
Year
(b) Cod harvested from Georges Bank

Figure 16.23 In the North Atlantic off the coast of Newfoundland, commercial catches of Atlantic
cod have fluctuated over time. Catches increased with intensified fishing by industrial trawlers in the 1960s
and 1970s (a), but the fishery subsequently crashed, and moratoria imposed in 1992 and 2003 have not
brought it back. A similar pattern is seen in the cod catches at Georges Bank (b); industrial fishing produced
30 years of high catches, followed by a collapse and the closure of some areas to fishing. Note also that in each
case, there is one peak before 1977 and one after 1977. The first peak and decline resulted from foreign fishing
fleets, whereas the second peak and decline resulted from Canadian and U.S. fleets, respectively, after they laid
claim to their 200-mile exclusive economic zones. Data (a) from Millennium Ecosystem Assessment, 2005. Ecosystems and
human well-being: synthesis. World Resources Institute. Washington, DC. Used with permission and (b) O’Brien, L., et al., 2008.
Georges Bank Atlantic cod. An Assessment of 19 Northeast groundfish stocks through 2007. Northeast Fisheries Science Center,
Woods Hole, MA. 459

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