1
Introduction
Throughout the centuries fish has been an important component of the
population’s diet in many parts of the world. Fish catches increased
rapidly over the past hundred years due to improved technology,
which provided more powerful engines and sonar equipment. This led
to over fishing and caused a worldwide decrease in wild stocks. As a
result, the growth in fish catches stopped some 20 years ago. The need
to increase fish production by farming became therefore an urgent
matter.
The term ‘aquaculture’ covers all forms of cultivation of aquatic ani-
mals and plants in fresh-, brackish- and saltwater. Aquaculture has the
same objective as agriculture, namely, to increase the production of
food above the level that would be produced naturally. Today, aqua-
culture is responsible for an ever-increasing share of global aquatic
food production, which has increased from 3.9 percent in 1970 to 31.9
percent in 2003 (FAO, 2005).
This book focuses on the small-scale cultivation of mainly freshwater
fish species. As in agriculture, fish farming techniques include:
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Removal of unwanted plants and animals
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Replacement by desirable species of fish
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Improvement of these species by crossbreeding and selection
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Increase of nutrient availability by the use of fertilisers and feeds
Fish farming can be combined with agriculture, animal husbandry and
irrigation practices, which can lead to better utilisation of local re-
sources and ultimately to higher production and net profits. This prac-
tice is called ‘integrated fish farming’ and the subject is extensively
dealt with in Agrodok No. 21.
The most important advantages of fish farming are summarised below
and depicted in figure
Advantage of fish farming
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Fish provides high quality animal protein for human consumption.
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A farmer can often integrate fish farming into the existing farm to create
additional income and improve its water management.
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Fish growth in ponds can be controlled: the farmers themselves select the
fish species they wish to raise.
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The fish produced in a pond are the owner's property; they are secure and
can be harvested at will. Fish in wild waters are free for all and make an in-
dividual share in the common catch uncertain.
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Fish in a pond are usually close at hand.
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Effective land use: effective use of marginal land e.g. land that is too poor,
or too costly to drain for agriculture can be profitably devoted to fish farm-
ing provided that it is suitably preparation
Fish farming practices
2.1
Methods of fish farming
Fish farming may range from ‘backyard’ subsistence ponds to large-
scale industrial enterprises. Farming systems can be expressed in
terms of input levels (figure 2).
In extensive fish farming, economic and labour inputs are usually low.
Natural food production plays a very important role, and the system’s
productivity is relatively low. Fertiliser may be used to increase fertil-
ity and thus fish production.
Semi-intensive fish farming requires a moderate level of inputs and
fish production is increased by the use of fertiliser and/or supplemen-
tary feeding. This means higher labour and feed costs, but higher fish
yields usually more than compensate for this.
Intensive fish farming involves a high level of inputs and stocking the
ponds with as many fish as possible. The fish are fed supplementary
feed, while natural food production plays a minor role. In this system,
difficult management problems can arise caused by high fish stocking
densities (increased susceptibility to diseases and dissolved oxygen
shortage). The high production costs force one to fetch a high market
price in order to make the fish farm economically feasible.
The focus of this Agrodok is on extensive and semi-intensive fish
farming practices.
Pond culture
The majority of freshwater fish are raised in ponds. Water taken from
a lake, river, well or other natural source is channelled into the pond.
The water either passes through the pond once and then it is dis-
charged, or it may be partially replaced so that a certain percentage of
the total water in a system is retained. Pond systems that yield the
highest fish production only replace water lost through evaporation
and seepage. Water flow generally reduces the production of pond sys-
tems in the tropics.
Fish farming ponds range in size from a few dozen square metres to
several hectares (ha). Small ponds are normally used for spawning and
baby fish production, while larger ponds are used for the grow-out
period. Production ponds larger than 10 ha become difficult to manage
and are not very popular with most producers. The ponds illustrated
here serve only as examples. The kind of pond a farmer will build de-
pends very much on local resources, equipment and conditions.
Ponds are usually located on land with a gentle slope. They are rec-
tangular or square-shaped, have well-finished dikes and do not collect
run-off water from the surrounding watershed (see figure 17). It is im-
portant that sufficient water is available to fill all the ponds within a
reasonable period of time and to maintain the same pond water level.
You should also be able to drain the pond completely when the fish
are to be harvested. Side slopes should be 2:1 or 3:1 (each metre of
height needs 2 or 3 metres of horizontal distance), which allows easy
access to the pond and reduces the risk of erosion problems.
To prevent fish theft, try to locate the pond as close to your home as
possible. Another method to keep thieves away from your fish pond is
to place bamboo poles or branches in the water, which makes netting
and rod-and-line fishing impossible. Apart from theft prevention, the
poles and branches provide the fish with extra natural food. This prac-
tice is called periphyton-based fish farming and will be described in
detail in chapter 3.
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