The issue
In the process of producing food, economic
resources, employment, livelihood and recreation,
fisheries modify ecosystems through more or less
reversible impacts on the target resource itself
(including through overfishing), the species
associated to or dependent on it (such as predators
or preys), on the trophic relationships within the
ecosystem in which the fishery operates, and on the
habitat. The fishery sector is expected to reduce
these impacts to a minimum that would also be
compatible with its own existence.
Some of the more well-documented impacts
include:
Overfishing excessive fishing reduces
spawning biomass below optimum levels and catches
below the maximum sustainable yield. The problem,
systematically addressed for a century albeit with
mixed results, began in the North Atlantic before
World War II and spread progressively to the North
Pacific in the 1950s, the Eastern Atlantic and
Eastern Pacific in the 1960s, the Indian and
Antarctic oceans in the 1970s and the South Pacific
and Southwest Atlantic in the 1980s - all with very
significant economic costs.
Changes in species composition and
biodiversity are common with progressive
reduction of large, long-lived, and high value
predator species and the increase in small,
short-lived, and lower value pelagic and demersal
prey species. The process has been coined as
"fishing down the food chain". Important
macroscopic changes have been observed in many
ecosystems such as the North Sea, Yellow Sea, North
Atlantic (e.g. George's Bank and Barents Sea), Gulf
of Thailand, and Southeast Australia In some
regions, the abundance of scavenging birds has
significantly increased, possibly due to the large
quantities of discards. It is now also clear that
intensive fishing reduces genetic diversity of wild
populations (e.g. rapidly depressing the proportion
of fast growing and late spawning individuals).
Changes in species composition or dominance can
also be provoked through competition for food
between fisheries and marine apical predators.
Non-selective fishing gear (e.g. trawls,
longlines, gillnets) can take a significant bycatch
of juvenile fish, benthic animals, marine mammals,
marine birds, vulnerable or endangered species,
etc. that are often discarded dead (about 20
million tonnes per year). While bycatch and discard
problems are usually measured in the potential loss
of human food, the increased risk for particularly
vulnerable or endangered species (e.g. small
cetaceans, turtles) is significant. In the North
Sea, for example, the impact on the food chain and
species composition is consequential as discards
can represent up to 30% of birds' consumption.
Ghost fishing occurs when certain gear
such as pots or gillnets continue to kill fish for
some time after having been discarded at sea or
lost, e.g. in bad weather.
Impacts on the bottom result from the
intense use of trawls and other mobile bottom gear
(e.g. dredges) result in changes in bottom
structure, microhabitats, and benthic fauna. The
effect is particularly obvious when these gears are
used in environments such as sea grass and algal
beds, coral reefs, sponges, tube worms. The
long-term impact is less obvious on soft bottoms
although scraping and ploughing the bottom to
depths of as much as 30 cm can seriously disturb
the substratum habitat and productivity.
Destructive fishing practices have also
spread in some poor coastal communities (e.g. the
use of dynamite and poison) particularly on coral
reefs. Other less conspicuous or debated impacts
relate to direct dumping of debris (gear, twine,
food containers, plastic bands, etc.) by fishing
fleets, including organic pollution by at-sea
processing factory ships, coastal pollution of
processing plants, contribution to global warming
through exhaust fumes and refrigerant gases, and
accidental introduction of alien
species.
Possible solutions
Overfishing is the central problem in fisheries
management and must be tackled through better
control of fishing capacity and specific resource
rebuilding plans. The same set of measures would
also improve species composition although it is
impossible to exploit the ecosystem without
affecting the relative importance of different
species. Selectivity can be improved and impacts on
the bottom and habitat can be reduced through
better gear technology and improved fishing
practices. Ghost fishing can be decreased through
greater awareness raising, prohibition and control
of dumping of damaged gear at sea, as well as
active at-sea programmes for retrieval of lost
gear. Gear technology can also contribute in
diminishing the fishing capacity of lost gear (e.g.
biodegradable material, collapsible traps, etc.).
Destructive fishing practices must be
further prohibited with stronger enforcement.
Overall, however, the solution is also in generally
improving the economic conditions of poor coastal
communities and providing alternative forms of
livelihood. In general, substantial efforts are
needed to improve data collection and research on
these issues.
Action taken
Countries have been tackling overfishing for a
long time, although not very successfully. On the
institutional side, NGOs have become very active at
uncovering and illustrating the problem, exerting
considerable pressure on governments and
international fishery organizations. An
International Plan of Action (IPOA) for the
Management of Fishing Capacity was adopted at FAO
in 1999 and is currently being implemented. In
addition, the FAO IPOA on Illegal, Unreported and
Unregulated Fishing (IUU), adopted in 2001 will
also contribute to countering overfishing. In order
to limit international trade in endangered fishery
species, CITES is considering adding to its annexes
fish species subject to large-scale exploitation.
The progressive development of ecolabelling
practices and the increasing integration of
environmental criteria into sustainability criteria
for fisheries should also provide additional
incentives and fuel consumers' pressure.
On the operational side, much has been done to
address the environmental impacts of fisheries.
Some countries have regulated discarding, imposing
severe quotas, or banning it altogether, forcing
the landing of all unwanted bycatch (e.g. in
Norway, Canada, Iceland, and the Faeroe Islands).
Selective grids, panels and square meshes are used
in several trawl fisheries to facilitate the escape
of unwanted species or small-sized individuals.
Longlines are being modified to reduce bycatch of
birds and an IPOA for Reducing Incidental Catch of
Seabirds in Longline Fisheries was adopted by FAO
in 1999. Special devices are currently used in tuna
fisheries to successfully reduce dolphin catches.
Zoning has been conventionally used to keep
trawlers away from vulnerable coastal habitats,
although with little success in areas with large
overcapacity. Marine Protected Areas (MPAs)
have become fashionable and if properly enforced
could be more effective. In some countries (e.g.
Norway), programmes exist to retrieve lost gillnets
lying on the bottom. Programmes for the development
of integrated and more sustainable
livelihoods are being implemented (e.g. by FAO
in Western and Central Africa). Some countries
(USA, Ireland) require the elaboration of an
environmental impact assessment (EIA) and/or
environmental impact statement (EIS) for
their fisheries.
Outlook
Awareness of this issue has been greatly
increasing since UNCED (1992) both in the fisheries
sector and among the public. The general pressure
and progressive evolution towards ecosystem-based
fisheries management will facilitate the reduction
of environmental impacts. The sector is quite
willing to act positively if this can be done in an
economically viable way. Progress made in fishing
and processing technology is significant and the
position of the fisheries sector regarding
ecolabelling is gradually improving. As a
consequence, while much remains to be accomplished,
the prospects for improvement are optimistic.
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