Page 457 - Environment: The Science Behind the Stories

100 Figure 16.19 After rising
China for decades, the total global
fisheries catch has stalled
World, excluding China
80
Capture fisheries (millions of metric tons) 60 scientists fear that a global
for the past 20 years. Many
decline is imminent if conservation
measures are not taken. The figure
40
shows trends with and without
China’s data, because research
20
suggests that China’s data may
be somewhat inflated. Data from the
0 Food and Agriculture Organization of the
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 United Nations, 2012. The state of world
Year fisheries and aquaculture 2012. Fig 3.

yield more than they are already yielding without being driven they played. In the Caribbean, green sea turtles ate sea
into decline. grass and likely kept it cropped low, like a lawn. But with
Total global fisheries catch, after decades of increases, today’s turtle population a fraction of what it was, sea
leveled off after about 1988 (Figure 16.19), despite grass grows thickly, dies, and rots, giving rise to sea grass
increased fishing effort. In 2008, the FAO concluded that wasting disease, which ravaged Florida Bay sea grass in
“the maximum wild capture fisheries potential from the the 1980s. The best-known case of historical overharvest-
world’s oceans has probably been reached.” Fishery col- ing is the near-extinction of many species of whales. This
lapses such as those off Newfoundland and New England resulted from commercial whaling that began centuries ago
are ecologically devastating and take a severe economic and was curtailed only in 1986. Since then, some species
toll on human communities that depend on fishing. A com- (such as the humpback whale) have been recovering, but
prehensive 2006 study in the journal Science predicted that others have not.
if current trends continue, populations of all ocean species Groundfish in the Northwest Atlantic historically
that we fish for today will collapse by the year 2048. If were so abundant that the people who harvested them
fisheries collapse as predicted, we will lose the ecosystem never imagined they could be depleted. Yet careful his-
services they provide. Productivity will be reduced, eco- torical analysis of fishing records has revealed that even
systems will become more sensitive to disturbance, and in the 19th century, fishers repeatedly experienced locally
the filtering of water by vegetation and organisms (such as dwindling catches, and each time they needed to introduce
oysters) will decline, making harmful algal blooms, dead some new approach or technology to extend their reach and
zones, fish kills, and beach closures more common. Aqua- restore their catch rate.
culture (raising fish in tanks or pens) is booming and is
helping to relieve pressure on wild stocks, but fish farm-
ing comes with its own set of environmental dilemmas Fishing has industrialized
(pp. 269–270). All this makes it vital, many scientists and
fisheries managers say, that we turn immediately to more Today’s industrialized commercial fishing fleets employ fos-
sustainable fishing practices. sil fuels, huge vessels, and powerful new technologies to
capture fish in great volumes. Factory fishing vessels even
process and freeze their catches while at sea. The global reach
We have long overfished of today’s fleets makes our impacts much more rapid and
intensive than in the past.
People have always harvested fish, shellfish, turtles, seals, The modern fishing industry uses several methods to
and other animals from the oceans. Much of this harvesting capture fish at sea that are highly efficient but also environ-
was sustainable, but scientists are learning that people began mentally damaging. Some vessels set out long driftnets that
depleting some marine populations centuries or millennia span large expanses of water (Figure 16.20a). These chains
ago. Overfishing then accelerated during the colonial period of transparent nylon mesh nets are arrayed to drift with cur-
of European expansion and intensified further in the 20th cen- rents so as to capture passing fish, and they are held vertical
tury. At each stage, improved technologies and increasingly by floats at the top and weights at the bottom. Driftnetting
global markets intensified our impact. usually targets species that traverse open water in immense
Recent syntheses of historical evidence by marine schools, such as herring, sardines, and mackerel. Specialized
biologists and historians reveal that ancient overharvest- forms of driftnetting are used for sharks, shrimp, and other
ing likely affected ecosystems in ways we only partially animals.
understand today. Large animals, including the Caribbean Longline fishing (Figure 16.20b) involves setting out
monk seal, Steller’s sea cow, and Atlantic gray whale, were extremely long lines (up to 80 km [50 mi] long) with up to
hunted to extinction prior to the 20th century—before sci- several thousand baited hooks spaced along their lengths. Tuna
456 entists were able to study them and the ecological roles and swordfish are among the species targeted by longline fishing.

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