Regulatory measuresmay then be adopted
upon comparison ofthe predicted environ-
mental concentration (in water, sediments
and organisms) and the information on
lowest concentration where adverse bio-
logical effects can be expected.
As for pollution control of African
waters, for which e,cotoxicological data are
scarce, Biney et al. (1987) list the following
strategy options for the management of
polluting discharges:
Limitation of the effluentby means
of rigid eMuent standards, both
with chemical concentration lim-
its andlor with a toxicologicallimit
derived by simple acute toxicity
tests on effluent. However, the
specific characteristics of the re-
ceiving waterbody are not consid-
ered.
Limitation of the effluent by flex-
ible standards. Here, the limits
are calculated in order to main-
tain water quality criteria in a
specific waterbody. Also, in this
case, the limit can be defined as
a threshold of the chemical and/
or its toxic effects.
For some chemical substances it
is scientifically unsound and in-
sufficient for environmental pro-
tection to set up objectives, crite-
ria and regulations for water alone.
The classical case is mercury
(Moore and Ramamoorthy 1984).
In such cases, it is necessary to
indicate objectives or criteria for
another environmental compart-
ment (e.g., sediments andlor fish).
In some cases, where a species is
shown to be particularly sensitive
to certain substances (e.g., crus-
taceans to pesticides), an "indica-
tor speciesn-orientedmanagement
strategy has to be preferred to the
water quality criteria approach
(Hellawell 1986).
The classification of chemical
substances in use in a country into
"black", "grey" and "white" lists
can be of help (Hellawell 1986),
especially in the framework of a
hazard assessment approach to
water quality control, i.e., the
comparison of predicted environ-
mental exposure with available
toxicity data. This does not nec-
essarily mean that blacklisted
chemicals are to be totally banned,
but that they should be used only
under certain conditions and strict
controls.
In summarizing, it is emphasized that
the particular role of aquaculture in uti-
lizing land and water resources for food
production calls for an integrative and
flexible environmental legislation which
is enforceable, effective and adaptive to
the socioeconomic conditions and develop-
ment needs in local communities, particu-
larly as prevailing in developing coun-
tries. Modern scientific methodologies and
conceptual frameworksfor the assessment
and prediction of environmental impact
are being developed and should be applied
in environmental management and regu-
lation of human activities, including
aquaculture.Institutional Aspects
During the last decades there has been
an increasing awareness that environ-
mental protection cannot succeed as an
isolated activity. Biswas (1978) stressed
that planning and management of water
development projects should be such that
the economic benefits are maximized
without causing serious impacts on the
environment. In addressing preventative
control of water pollution in developing
countries, Diamant (1 978) emphasized the
need for simultaneous planning of water
supply and wastewater disposal projects,
for water pollution control legislation and