The essential features of a standard fish pond include:
- Core trench.
- Distribution channel.
- Spill way.
- Dam slope (inner and outer).
- Dam: This is the large area of the pond that holds water. It ensures the availability of water in the pond.
- Core trench: This is the escavated portion of the fish pond. It consolidates the walls with stones and cement.
- Distribution channel: This is the area which helps to introduce water into the pond. Water is distributed to all the sections of the pond until it gets to a particular volume. Fertilizers can equally be mixed up with the water and distributed together.
- Spill way: This is a passage for water to flow over or around a dam. It is positioned at one end of the dam. It uses wood or wire-mesh screen.
- Monk: The monk regulates water level automatically in the pond. It helps in the discharge of water from both the surface and bottom. It has vertical low and horizontal culverts or pipes. They are constructed with concrete.
- Boards: These are structures which regulate the flow of water. They are made up of desirable wood and also hold water inside the pond. They are fitted at the centre or middle of slabs at the gates.
- Screens: These structures help to prevent the entry of undesirable species of fish into the pond. They also prevent fish movement out of the pond.
- Dam slope (inner and outer): This helps to regulate water movement into and out of the pond. It also ensures the availability of water in the pond. It is usually constructed at the beginning and end of the pond.
ESTABLISHMENT/CONSTRUCTION OF A FISH POND
The following operations are normally carried out when establishing a fish pond:
- Site selection: Site selection involves the choice of best site based on necessary conditions like a piece of land through which a perennial stream flows. The site should be on a fertile and clay soil to prevent seepage of water. It should have a valley with narrow neck and at a fairly open area.
- Reconnaissance or general survey: Detailed survey of the chosen site should be carried out, especially by extension workers. Such workers help to determine the height of pond, volume of earth to be used for dyke, total water surface area, volume of water in the pond or embarkment.
- Clearing and stumping of site: This involves the removal of thrash, cutting of trees and removal of stumps.
- Construction of dam: Dam is usually constructed across the stream. Materials used in the construction should be of good quality. Clay soil should be used for dam construction because of its ability to hold water.
- Construction of core trench: This involves the removal of the soil or excavation. It is positioned at right angle to the dam. Such dam should be made with consolidated stones or cement walls.
- Construction of spill way: Spill way is positioned at one end of the dam. Wood and wire-mesh screen should be used to construct the spill way.
- Impoundment of pond: This involves the filling of the pond with water by opening the monk board of the reservoir. This leads to the release of water and flow to fill the pond.
- Liming: This involves the addition of limestone or calcium carbonate powder to the sides and bottom of the pond to seal pores and prevent water loss. Liming also reduces acidity of the pond water and encourages the growth of planktons fish food). However, liming is done before filling the pond with water. The lime materials should be left for four weeks in its dry state.
- Pond fertilization: Fertilizer encourages the growth of planktons (fish food). Pond fertilization is done by pouring organic fertilizers such as poultry droppings, cow dung or the use of inorganic ones like N.P.K. or super phosphate. Pond fertilization should be carried out 15 days before stocking pond with water.
- Pond inoculation: This is the introduction of proper plankton species into the pond. This is done by obtaining some water from a plankton-rich pond and pour into a newly fertilized pond. When the pond water begins to turn green, this green water indicates the abundance of planktons (natural food of fish). To keep the water green, fertilizer is added into the pond every week.
- Stocking of pond: This is the introduction of the proper baby fish called fingerlings or fries into the pond. The pond is stocked at the rate of two fingerlings per square metre. The fingerlings should not be poured into the pond. Rather, the container should be placed gently into the water and the fingerlings allowed to swim into the water pond themselves.
MAINTENANCE OF A FISH POND
To ensure the continuous availability of fish in a fish pond or maintain high fish yield, it is necessary to ensure:
- Regular feeding: The fish must be fed twice daily from selected point(s). Supplementary feed in the form of compound feed should be given in sufficient quantity to ensure rapid growth and early maturity of the fish.
- Deweeding: This is the removal of weeds from the pond. It allows the dissolution of oxygen in water, the penetration of sunlight to the bottom of the pond which will promote the growth of fish food (planktons). It also prevents the build-up of pests and diseases.
- Desilting: This is the removal of silt or prevention of silt from entrying into the pond. Desilting makes the water to be clean, promotes easy movement of fish within the water and also prevents pollution of the water.
- Aeration: Aeration enables oxygen to dissolve in water which is required by fish for respiration. Fishes usually come to the surface of water due to lack of oxygen in the water. Weeds, excessive organic manure, overstocking, etc prevent proper aeration of the pond.
- Constant supply of water: The pond should always be filled with water and any leakage repaired.
- Control of predators: Predators like birds and snake should be prevented from entry into the pond because they could eat up the fish in the pond. This can be done by keeping the pond’s surrounding clean (i.e. constant weeding).
- Prevention of diseases: Diseases should be prevented as this could kill all the fish in the pond. Adequate feeding, stocking, temperature, manuring, weeding, etc help to prevent diseases.
- Regular harvesting: Regular harvesting of fish is necessary to prevent over-population, outbreak of diseases and cannibalism. Periodic or total harvesting could be done six months after stocking, using net or by draining of the pond.
- Regular application of fertilizer: This should be done once in a month to promote the growth of fish food (planktons) in the pond.