Lesson Note
Subject: Agricultural Science
Topic: Aquaculture
Sub Topic: Establishment of Fish Pond
Lesson Objectives: By the end of the lesson, the learners should be able to:
- Define a fish pond,
- State the conditions or factors necessary for siting a fish pond,
- Identify the features of a standard fish pond,
- State the various operations carried out when establishing or constructing a fish pond,
- Establish or construct a fish pond.
LESSON SUMMARY/DISCUSSION
A fish pond is a controlled, small artificial lake or retention basin that is stocked with fish and is used in aquaculture for fish farming, for recreational fishing, or for ornamental purposes.
CONDITIONS OR FACTORS NECESSARY FOR SITING A FISH POND
- Adequate water supply
- Soil in the area.
- Vegetation of the area.
- Topography of the area.
- Availability of fast growing fishes.
- Availability of supplementary feedstuff.
Adequate water supply: There must
be constant supply of water of good
quality and quantity. The water can be
from streams, lakes, rivers, irrigation
canals and springs. Good quality water is necessary because it will provide oxygen and food to fish, create a medium for waste discharge and reproduction. The water should not have a bad smell, taste or colour and should not be too muddy and must be free from pollution.
Soil in the area: Soil in the area must
be fertile so as to supply nutrients to the fish. It should be clay because of its ability to hold water which is very important in fish pond construction. Soil with too much sand or gravel is not good and would not retain water.
Vegetation of the area: Low vegetation, especially grasslands are preferred. Woody sites are not suitable because clearing and stumping will greatly increase the cost of setting up the fish pond.
Topography: The shape of the land
should allow for easy draining and filling of pond with water. The water must flow from a place that is higher than the pond so that the water can flow into the pond directly. If not, the need for water pumps would arise and this will increase the cost of the project. However, fish pond can be constructed on a flat or level ground but lots of soil have to be removed to create the slope.
Availability of fast growing fish:
Fingerlings or baby fish for stocking a
fish pond should be the type that can
grow fast and mature within a very short time. The use of improved varieties (breeds) in stocking fish pond makes fish farming more profitable.
Availability, of supplementary
feedstuf: Supplementary feeding is
done to ensure rapid growth offish and allow high stocking density. Artificial or compounded feeds in form of pellets are used to supplement the natural feed
(planktons). The addition of fertilizers
also promotes the rapid growth of
planktons (natural fish food) in the pond.
FEATURES OF A STANDARD FISH POND
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 to prevent 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 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.
Reconnaisance 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.PK. 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 fingerings 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 s 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 e.t.c 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 draning 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.
LESSON EVALUATION
1. Describe a fish pond.
2. What are the factors to be considered when siting a fish pond?
3. What are the features of a standard fish pond?
4. State the various ways to maintain a fish pond.