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Many of the resources that aquaculture depends
on are finite - water, land; inputs like seed,
broodstock, feed ingredients. It is essential that
the sector's resource use is managed so as to
achieve long term sustainability and, in most
cases, this means avoidance of adverse effects on
the environment. At the same time, there are often
conflicting demands on the resources aquaculture
uses from other economic sectors; management
decisions must then be made on the most appropriate
distribution of what is available. The concept of
economic efficiency can be useful in this process.
In many cases aquaculture can be one of the most
efficient users of resources in terms of the
outputs it generates from a particular input - such
as water, for instance. At the farmer level
'efficiency' can mean profitability and, as long as
the inputs and outputs are given their proper
value, sustainability also.
Decisions on resource use do not necessarily
have to favour one sector at the expense of
another. Aquaculture activities can frequently be
integrated with other uses of water and land. Much
aquaculture production occurs in small freshwater
ponds that often have multiple uses. Fish
production may be integrated with household waste
disposal, poultry rearing or vegetable growing. In
some cases, a pond may just be a by-product of an
excavation to provide soil for house construction
or road building. In other situations, aquaculture
may be developed on land that is unsuitable for
agriculture, due to the soil's low nutrient
content, salinization or because of flooding.
In some kinds of aquaculture, integration with
other interests can be more difficult. Balancing
the farming of sea fish in cages or of oysters on
moored systems in the sea, for instance, with the
demands of tourism or fishing can be problematic.
It is especially important in these cases that
national and regional authorities develop a well
thought out management plan, that this plan is
prepared with the participation of the stakeholders
and that it meets the aims of optimizing economic
efficiency and sustainable use of the available
resources.
The zoning of water and land areas for
particular kinds of use, based on their physical
characteristics and limitations, can be a useful
start in the management process. It is also
important that an understanding is reached of the
social, environmental and biological constraints
that exist. Problems have occurred with the
expansion of shrimp farming, for instance, because
of too narrow a focus in the planning process.
Areas of land may have suitable soils, topography,
ground cover etc. for development as shrimp ponds,
but it is important neither to ignore the capacity
of the local coastal environment to accept and
reprocess the effluents that would be produced, nor
the potential impacts on coastal peoples. Similarly
in the salmon cage culture industry, it was not
initially realized that disease considerations
would set lower cage density limits than would be
expected merely on the basis of prudent management
of dissolved oxygen levels and feed inputs.
Aquaculture operations need seedstock and
ideally these should come from hatcheries operating
captive breeding programmes, without using animals
captured from the wild. This first step towards
domestication has been taken with comparatively few
farmed species however. Management of the
collection of wild stocks is a noted problem
particularly in the shrimp, eel, and some sectors
of the salmon farming industries. It is arguable
that the collection of some seed from the wild, for
instance of oyster spat, has no adverse effects on
wild stocks and so guidelines have to be considered
on a species by species basis, but the overall goal
of domestication has merit.
Currently, there are also serious issues to be
addressed as a result of the transfer of broodstock
and seed stocks between regions and even
continents. Disease and competition problems have
resulted from many imprudent introductions and this
is a key area that needs well-informed management.
Scientists have worked to develop safe guidelines
to assist managers in this area. (see
DIAS)
The management of feed and effluents are further
important factors in optimizing aquaculture's
resource use and minimizing adverse effects on
local environments. The sources and costs of feed
and feed ingredients affect the economic efficiency
of production systems. The sinks where wasted and
uneaten feed ends up always need consideration, but
there should also be effort made towards avoiding
the use of ingredients for feed that could have
been used directly for human food. Secondly,
formulations should strive to minimize net nutrient
and faecal output. The technology exists to run
many kinds of aquaculture so that the effluents
contribute no net increase in nutrient load to the
natural environment. While some sectors face
practical or economic difficulties in achieving
this, it is desirable that management strategies
work towards it as a goal.
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