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Spanish).Discussion
ROSENTHAL: This paper clearly highlights three
areas of concern: 1. the resource systems in which
aquaculture takes place andthe environmental quality
therein: 2. the environmental cunditions within the
farminisystemitself; and% the effect that aquaculture
activities can have on surroundinn - environments.
The concept of assimilative capacity isinteresting
but can be risky. For example, industrial operations
often try to push waste receiving capacity to its limits
and we are hardly able to set safe limits. For this
reason, the various conventions concerned wilh the
North Seahave controversially debated the options to
define its assimilative capacity. ICES at present feels
unable to adopt this approach because of the many
interactions among environmental factors (natural
and from pollution) about which we know little.
Scientists can therefore beat helo society and its
environmental regulatory authorities by doc~menting
environmental change while politicians will have to
decide what chanGs are acceptable to society.
Politicians usually want scientists to set benchmark
numbera, but this can be difficult and is oken
dangerous.PULLM: The paper is concerned almost exclusively
with the freshwater environment. Freshwatcr is
becomingavery limitedresource. It isuscd for inigation
and domestic supply and wastewater disposal.
Freshwater aquaculturn may become less and less
viable if it competes with rather than complcments
these uscs, especially close to the huge and rapidly
growing cities of some developing countries. For
example, Laguna de Bay, the 90,000 ha Reshwater
lake adjacent to Metropolitan Manila and famous for
its cage and pen aquaculture, will probably have to
supply some of the city's drinking water in future.ROSENTHAL: So again, wemust mnsidcr thc dynamic
nature ofthese situations and the multiple usc options
involved when wc asscss sustainability.BILIO: In Africanreservoir sthat areused for drinking
water supply, aquaculture is generally prohibited.
Only fisheries are allowed. If the purpose of such
reservoirs is for irrigation or power generation,
however, both aquaculture andculture-basedfisheries
are possible. One prerequisite for such culture-based
fisheries is to know in advance the characteristics of
the catchment area (geology and limnology).MART~NEZ-ESPINOSA: This assimilative capacity
approach, although not yet fully formulated has a
flexibility that no other approach has ever had. It is
based on the situations of various cases. For example,
if a trout farm effluent causes eutrophication in a
freshwater body used for drinking purposes, this is
aerious. If, however, it goes almost directly into the
sea, it is less serious. This is a site-specific approach.
This illustrates why we are recommending it.EDWARDS: You mentioned integration of intensive
aquaculture with agriculture. We can also mnceive
using the elfluente fmm intensive aquaculture in less
intensive aquaculture, such as semi-intensive ponds
containing filter-feeding fish - bearing in mind Dr.
Pullin's comment about water scarcity. Of murse, the
other resources, especially land, and the farmers' and
consumers' interest in these species have also to be
there, but at least this seems theoretically feasible.MART~EZ-ESPINOSA: We must be careful though
not to attempt to introduce too many new and
demanding technolohies into rural areas when trying
to develop 'socially-orionlcd' aquaculture. Too many
projects ignore this and bring in, for example, biogas
and wind power technologies.EDWARDS: I totally agree. Such technologies rarely
get beyond the drawing board or prototype
development in most rural development projects. I
was referring specifically to the productive reuse of