Site selection
Proper selection of a site is probably the most important factor for success. However, if the ideal site is not available, you may have to compromise. There may also be conflicts concerning land and water use that need to be resolved. You should decide on which species to raise, based on the available feeds (e.g. agricultural by-products) and possible fertilisers (e.g. compost or animal manure). Site selection will depend on the type of fish farm you plan to run. For pond construction you need to consider the following factors: soil type and quality and quantity of the water available.
Soil
The quality of soil influences both water quality and productivity in a pond. The soil must also be suitable for dike construction. To determine soil suitability the two most important properties to examine are soil texture (particle size composition), and porosity or permeability (ability to let water pass through). The pond bottom must be able to hold water (have a low porosity, like clay) and the soil should also contribute to the fertility of the water by providing nutrients. The best soil for pond construction should contain a lot of clay.
The three methods one should follow to predict whether the soil will be suitable for pond construction are:
1. Squeeze method
Wet a handful of soil with just enough water to make it moist
Squeeze the soil by closing your hand firmly
If it holds its shape after opening the palm of your hand, the soil will be good for pond construction.
2. Ground water test
This test should be performed during the dry period in order to get reliable results:
Dig a hole to a depth of one metre
Cover it with leaves for one night to limit evaporation
If the hole is filled with ground water the next morning, a pond could be built but take into account that you will probably need more time to drain the pond. This is due to the high ground water levels that will refill the pond.
If the hole is still empty the next morning, no problems will occur as a result of high ground water levels and the site will probably be suitable for pond fish farming. Now you should test the soil permeability to water.
3. Water permeability test :
Fill the hole with water to the top
Cover the hole with leaves
The following day the water level will be lower due to seepage. The dikes of the hole have probably become saturated with water and might hold water better now.
Refill the hole with water to the top
Cover it once more with leaves. Check the water level the next day.
If the water level is still high, the soil is impermeable enough and is suitable for pond construction.
If the water has disappeared again, the site is not suitable for fish farming, unless the bottom is first covered with plastic or heavy clays.
Water
The availability of good water quality is significant for all fish farming systems but water quantity is of even greater importance for landbased fish farming systems. A constant water supply is needed, not only to fill the pond, but also to make up for the losses caused by seepage and evaporation .
Water temperature
Water temperature is an important condition in assessing whether the fish species selected can be raised. A water temperature between 20 °C and 30 °C is generally good for fish farming.
Water salinity
Variation in water salinity (amount of dissolved salts in the water) is also an important factor to consider. Some fish species can withstand a wider salinity range than others: e.g. tilapia and catfish can withstand a wide range from freshwater to seawater, while carp can only withstand freshwater. These are the most important water quality criteria for site selection. There are other important water quality characteristics, but these are more easily controlled by management measures (for example, dissolved oxygen, pH, etc.
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