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Aquaculture can be defined as the high-density production of
fish, shellfish and plant forms in a controlled environment.
Stocking rates for high-density aquaculture are typically
thousand fold greater than wild environments. Modern fish
culturists employ both open and close systems to raise fish.
Open systems, such as, the raceways (used in hatcheries of
both finfish and shellfish and also in eel, trout culture) are
characterized by rapid turnover of water. Closed systems are
commonplace in pond culture of carps, catfishes, tilapia, sea
bass, prawn and shrimp among others. Closed aquaculture
systems do not have rapid turnover of water, but do not have a
high surface to volume ratio facilitating exchange of gases,
nutrients, energy etc. with the surroundings. Such closed
system, which is intensified, with high-density aquaculture
forms the basis of concern.
The
different forms of high density aquaculture is quite
similar because they all obey the same set of physical and
chemical principles. These principles compose the subject
of water chemistry and its net result i.e. water
quality. Poor water chemistry leads to deterioration
of water quality, which causes stress to the organisms
being raised. Efficient feed conversion, growth and
marketability of the final product cannot occur unless the
pond system is balanced or in harmony with nature.
Therefore the overriding concern of the fish culturist is
to maintain, ‘balance’ or ‘equilibrium conditions’ with
respect to water chemistry and its natural consequence -
good water quality.
Water quality for aquaculturists refers to the quality of
water that enables successful propagation of the desired
organisms. The required water quality is determined by the
specific organisms to be cultured and has many components
that are interwoven. Sometimes a component can be dealt
with separately, but because of the complex interaction
between components, the composition of the total array
must be addressed. Growth and survival, which together
determine the ultimate yield, are influenced by a number
of ecological parameters and managerial practices. High
stocking density of fish or crustaceans in ponds usually
exacerbates problems with water quality and sediment
deterioration.
Wastes generated by aquaculture activity (faeces and
unconsumed feed) first settle in the bottom and as a
consequence, organic waste and metabolites of degraded
organic matter is accumulated in sediment and water. Such
type of adverse pond conditions can be restored by
applying Water Quality Enhancing Formulations.
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