A guide for planners and managers - IUCN

Introduction
In many parts of the world, seafood supplies most of the protein and much of
the livelihood for large populations of people (Figure 4). In Africa artisanal fisheries
provide the bulk of the fish eaten by local people, but these fisheries are widely
considered to be fully exploited (Brainerd, 1994; Hatziolos et al., 1994; Insull et al.,
1995; Tvedten & Hersoug, 1992), with some being exploited beyond the level of
sustainability. But because fisheries are typically not managed for sustainability,
their contribution to national diets and income is diminishing and is likely to continue
diminishing.
Past and present overfishing
has led many of the world’s most
valuable fisheries to be seriously
depleted. Nor can it be assumed
that depleted stocks will recover to
reach their full potential. In fact,
this is most unlikely for several
reasons: juvenile fishes may
continue to be caught by
“industrial” fisheries and ground
up for animal feed; other species
may take the place of depleted
species and not yield to their
return; and habitats essential for
spawning or as nurseries may be
degraded or destroyed.
In addition to depleting fish, crustacean, and mollusc stocks, overfishing has
nearly extinguished certain species of whales, sea cows, and sea turtles. Many aquatic
animal groups are also under pressure because of incidental exploitation (bycatch);
that is, they are captured along with “target” species, killed, and discarded. An
example of this wasteful practice is the incidental capture and killing of sea turtles
in fishing nets in several countries, which threatens the survival of several species.
Preserving Biodiversity
FIGURE 4.
Fishermen at work; Inhaca Island, Mozambique.
Preserving diversity is a matter of both ethics and economic survival. For example,
genetic diversity (a component of biodiversity) is needed to sustain and improve
agricultural, forestry, and fisheries production, to keep future options open, to guard
against harmful environmental change, and to secure the raw material for much
scientific and industrial innovation.
For practical economic reasons, preserving biodiversity is necessary both to
secure food, fiber, and certain drugs and to advance scientific and industrial innovation.
Such preservation is also necessary to ensure that the functioning of ecological
processes is not impaired by loss of species. It is unlikely that other communities can
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Photo by John Clark.