245
in the USA, aquaculture contributes only to a tiny
fraction of total meat consumption and, that too,
only in the form of high-priced speciality items,
such as trout, crayfi sh and catfi sh. There are
countries (e.g . Israel) and specifi c industries (e.g.
mussel culture in Belgium, France and Spain) of
more than minor importance. However, the general picture, in the present time, in western
Europe, Africa and in North and South America is
one of a minor industry with unrealised potential.
15.6.1.2 Contemporary Aquaculture
Techniques
It may be noted here that two strategies are
basically employed by the nations which have
signifi cant aquaculture production:
(a) One approach is applied principally by
nations which have huge human population
vis-à-vis scarcity of animal protein. Such
nations generally grow fi shes, such as, carps
and mullets which occupy relatively low trophic positions, but grow rapidly in small,
confi ned areas, although they may not have a
high market price. These nations optimise
for large quantities of animal protein in preference to substantial economic profi ts.
(b) The second strategy is to grow lesser amounts
of high-quality, expensive products, such as
trout and shrimp. These organisms often are
carnivorous and usually require better care
(e.g. clean water, low densities and water
with a high dissolved oxygen content). As
such, this approach is generally used in
developed countries, such as the USA and
Japan. Nevertheless, a few developing countries have also experimented with this
approach to aquaculture with the expectation
for generating valuable export products.
Concomitant to above, contemporary aquaculture techniques, from a technical standpoint,
range from very simple manipulations of the
natural environment with little protection of the
culture organisms to extremely elaborate artifi -
cial environments which involve total control and
protection of the organisms. In view of this, the
simplest procedures are referred to as ‘extensive’
operations. They may consist merely of planting
seed oysters or clams on a suitable area of seabed
and then returning several years later to harvest
what remains. On the contrary, more control
can be obtained with a moderately ‘intensive’
procedure, such as the raft culture of oysters.
In this case, almost total protection is afforded
from benthic predators. Further, the raft may be
moved to fi nd more suitable feeding conditions,
better water quality, etc.
15.6.1.3 Ideal Culture Organisms
Ideally, a culture organism should have a simple
life history and have the capability of being
reared through all life history stages in captivity.
It is pertinent to mention here that a wide range of
both marine as well as FW organisms have been
tried as culture organisms. But only few have
proved to be both a biological and economic success. This is because most aquatic organisms
have one or more characteristics which make
them unsuitable for aquaculture.
15.6.1.4 Effi ciency of Aquaculture
It may be a common belief that fi sh could usually be raised more effi ciently, if a comparison
is made between fi sh farming and terrestrial
farming of domestic animals. However, in moderately intensive aquaculture, organisms are
usually fed with prepared supplementary fi sh
feeds, e.g. in pond culture of carps. In such situations, feed conversion rates of (ecological
growth effi ciency) for fi sh are about one-andhalf times as great as for swine and chicken
farming and almost twice as high as the conversion rates of cattle and sheep.
There could be two principal reasons for this
greater effi ciency:
1. Fish are cold-blooded vertebrates. As such,
they are not compelled to expend energy to
maintain a constant body temperature.
2. Fish are supported by water rather than by air.
Hence, they do not need to invest as much
energy in a heavy skeletal system or in constantly struggling the force of gravity. Energy
savings from both the factors could be incorporated into more effi cient growth and more
rapid weight gain.
Further, aquaculture usually provides higher
yields per unit area than agriculture in situations
15.6 Aquaculture
in the USA, aquaculture contributes only to a tiny
fraction of total meat consumption and, that too,
only in the form of high-priced speciality items,
such as trout, crayfi sh and catfi sh. There are
countries (e.g . Israel) and specifi c industries (e.g.
mussel culture in Belgium, France and Spain) of
more than minor importance. However, the general picture, in the present time, in western
Europe, Africa and in North and South America is
one of a minor industry with unrealised potential.
15.6.1.2 Contemporary Aquaculture
Techniques
It may be noted here that two strategies are
basically employed by the nations which have
signifi cant aquaculture production:
(a) One approach is applied principally by
nations which have huge human population
vis-à-vis scarcity of animal protein. Such
nations generally grow fi shes, such as, carps
and mullets which occupy relatively low trophic positions, but grow rapidly in small,
confi ned areas, although they may not have a
high market price. These nations optimise
for large quantities of animal protein in preference to substantial economic profi ts.
(b) The second strategy is to grow lesser amounts
of high-quality, expensive products, such as
trout and shrimp. These organisms often are
carnivorous and usually require better care
(e.g. clean water, low densities and water
with a high dissolved oxygen content). As
such, this approach is generally used in
developed countries, such as the USA and
Japan. Nevertheless, a few developing countries have also experimented with this
approach to aquaculture with the expectation
for generating valuable export products.
Concomitant to above, contemporary aquaculture techniques, from a technical standpoint,
range from very simple manipulations of the
natural environment with little protection of the
culture organisms to extremely elaborate artifi -
cial environments which involve total control and
protection of the organisms. In view of this, the
simplest procedures are referred to as ‘extensive’
operations. They may consist merely of planting
seed oysters or clams on a suitable area of seabed
and then returning several years later to harvest
what remains. On the contrary, more control
can be obtained with a moderately ‘intensive’
procedure, such as the raft culture of oysters.
In this case, almost total protection is afforded
from benthic predators. Further, the raft may be
moved to fi nd more suitable feeding conditions,
better water quality, etc.
15.6.1.3 Ideal Culture Organisms
Ideally, a culture organism should have a simple
life history and have the capability of being
reared through all life history stages in captivity.
It is pertinent to mention here that a wide range of
both marine as well as FW organisms have been
tried as culture organisms. But only few have
proved to be both a biological and economic success. This is because most aquatic organisms
have one or more characteristics which make
them unsuitable for aquaculture.
15.6.1.4 Effi ciency of Aquaculture
It may be a common belief that fi sh could usually be raised more effi ciently, if a comparison
is made between fi sh farming and terrestrial
farming of domestic animals. However, in moderately intensive aquaculture, organisms are
usually fed with prepared supplementary fi sh
feeds, e.g. in pond culture of carps. In such situations, feed conversion rates of (ecological
growth effi ciency) for fi sh are about one-andhalf times as great as for swine and chicken
farming and almost twice as high as the conversion rates of cattle and sheep.
There could be two principal reasons for this
greater effi ciency:
1. Fish are cold-blooded vertebrates. As such,
they are not compelled to expend energy to
maintain a constant body temperature.
2. Fish are supported by water rather than by air.
Hence, they do not need to invest as much
energy in a heavy skeletal system or in constantly struggling the force of gravity. Energy
savings from both the factors could be incorporated into more effi cient growth and more
rapid weight gain.
Further, aquaculture usually provides higher
yields per unit area than agriculture in situations
15.6 Aquaculture