developed without major changes, by
existing resource system structures?
What are the probable ecosystemic
and sociocultural costs involved in
this?
Another important consideration,
mainly for small-scale operations (but also
relevant to larger-scale aquaculture and
always location specific) is the target fish
yield set by development agencies for
aquaculture systems. This is often set too
high in the belief that the high yields
obtained by research institutions and
resource-rich farmers (for example,
10 t aha-l-year-l or more for semi-intensive
manured pond aquaculture) must also be
approached on farms, or else the
development is not worthwhile. For
existing fish farmers and potential new
entrants, especially in the poorest areas,
this is a counterproductive approach.
Modest yields from aquaculture can give
great nutritional and income improve-
ments in developing-country rural areas.
For example fishpond yields of 2 to 3
taha-year1 would be very attractive in
much of rural Africa.
What Kinds ofAquaculture
Make Sense in Developing
Countries?
The Brundtland Report gave these
encouraging words on aquaculture
development:
Aquaculture can be undertaken
in paddy fields, abandoned mining
excavations, small ponds and many
other areas with water, as well as on
various commercial scales: individual,
family, cooperative or corporate. The
expansion of aquaculture should be
given high priority in developing and
developed countries.
This is correct, but such aquaculture
development must be socially equitable,
environmentally compatible, and have
sufficient diversity and scope for change to
adapt to changing circumstances.
Intensive aquaculture (in effect, using
the feedlot principle) usually poses much
greater threats to the environment than
does extensive or semi-intensive
aquaculture. Intensive fish farms are
often heavy users of antibiotics and
disinfectants and their operators need to
be aware of the dangers of release of such
chemicals to the natural environment
including the possibilities of producing
drug-resistant pathogens (see Austin, this
vol.). Pollution by intensive aquaculture is
wellknown. Fishfecal wastes anduneaten
food in effluents from fish farms and in
settlement from cages have high biological
oxygen demands (BODS) and containlarge
quantities of particulate matter and
nutrients.
Such impacts greatly threaten
sustainability, but some less intensive
aquaculture systems can also be short-
lived (nonsustainable). The following
examples illustrate some of the relevant
issues.
Milkfish (Chanos chams) pen
aquaculture in Laguna de Bay, a shallow
90,000 ha eutrophic lake adjacent to
Metropolitan Manila, Philippines, grew
from a single experimental pen in 1970 to
about 7,000 ha of pens in 1974 producing
amean yield of about 7 taha-l year1 (Pullin
1981). They resembled extensive fish
'ranches' with some individual units as
large as 50 ha or more. At its peak, the
total pen area may have been as much as
34,000 ha. It is now about 2,800 ha and the
average annual yieldis about 3.8 t.haml. Its
expansion phase was a'goldrush'in which
the pen owners (mainly upper-class
citizens) got richer and the lake's small-
scale fishers and aquaculturists suffered
greatly. The decline has been because of
conflicts, losses due to typhoons and a
reduction in the lake's productivity
attributed to multiple causes (pollution,
turbidity due to catchment erosion, and
altered flushing patterns due to flood
control structures). This was a