9
18
47
21
1
Figure 17 (a) World fish
harvest 1950—1998 and (b)
the state of marine fish
stocks according to their
exploitation levels:
D depleted, O overexploited, F Fully
exploited, M Moderately
exploited, R Recovering
dealing with a new experiment not likely to be repeated. In the context of global
environmental change it is relevant to question whether the ecosystem effects of
fishing will affect the ability of marine ecosystem to cope with or/and adapt to
global change. We have no answer to this question beyond the limited logic
that a system under pressure may not bounce back if pressure is further increased.
Therefore my objective here is to briefly identify the major concerns regarding the
consequences of fishing from an ecosystem perspective.
Commercial fishing tends to focus on a species or group of species (target
species), but because fishing gears are not selective enough these are accompanied
in the catch by a number of secondary species, or by-catch. Most by-catch is
returned to the sea for economic, legal or personal reasons, largely in the form of
dead fish. It has been estimated that global discards are in the order of 17.9 and
39.5 million tonnes per year, a figure that varies heavily between fisheries
(Table 4). Shrimp and prawn fisheries discard up to 89% of their total catch while
pelagic fisheries like mackerel and sardine do not discard more than 10% of the
total catch, although this still equates to over a million tonnes of fish per year. A
substantial proportion of these discards, perhaps over 75%, is not lost, being
consumed by higher predators like seabirds and mammals. By-catch is
arguably the biggest problem faced by the world’s fisheries, both from a
management point of view and from an ecological point of view.
Like excessive by-catch, intensive fishing also changes the structure of
communities if the frequency of extraction is shorter than the generation time of
D. Pauly and V. Christensen, Nature, 1995, 374, 255—257.
D. L. Alverson, in Global Trends: Fisheries Management, eds. E. K. Pikitch, D. D. Huppert and
M. P. Sissenwine, 1997, Amer. Fisheries Society Symposium, 20, MD, USA.
A. V. Hudson and R. W. Furness, J. Zool., 1988, 215, 151—166.
M. Barange
78
18
47
21
1
Figure 17 (a) World fish
harvest 1950—1998 and (b)
the state of marine fish
stocks according to their
exploitation levels:
D depleted, O overexploited, F Fully
exploited, M Moderately
exploited, R Recovering
dealing with a new experiment not likely to be repeated. In the context of global
environmental change it is relevant to question whether the ecosystem effects of
fishing will affect the ability of marine ecosystem to cope with or/and adapt to
global change. We have no answer to this question beyond the limited logic
that a system under pressure may not bounce back if pressure is further increased.
Therefore my objective here is to briefly identify the major concerns regarding the
consequences of fishing from an ecosystem perspective.
Commercial fishing tends to focus on a species or group of species (target
species), but because fishing gears are not selective enough these are accompanied
in the catch by a number of secondary species, or by-catch. Most by-catch is
returned to the sea for economic, legal or personal reasons, largely in the form of
dead fish. It has been estimated that global discards are in the order of 17.9 and
39.5 million tonnes per year, a figure that varies heavily between fisheries
(Table 4). Shrimp and prawn fisheries discard up to 89% of their total catch while
pelagic fisheries like mackerel and sardine do not discard more than 10% of the
total catch, although this still equates to over a million tonnes of fish per year. A
substantial proportion of these discards, perhaps over 75%, is not lost, being
consumed by higher predators like seabirds and mammals. By-catch is
arguably the biggest problem faced by the world’s fisheries, both from a
management point of view and from an ecological point of view.
Like excessive by-catch, intensive fishing also changes the structure of
communities if the frequency of extraction is shorter than the generation time of
D. Pauly and V. Christensen, Nature, 1995, 374, 255—257.
D. L. Alverson, in Global Trends: Fisheries Management, eds. E. K. Pikitch, D. D. Huppert and
M. P. Sissenwine, 1997, Amer. Fisheries Society Symposium, 20, MD, USA.
A. V. Hudson and R. W. Furness, J. Zool., 1988, 215, 151—166.
M. Barange
78