Embankment is a form of pavement made on the side of the fish pond. It serves to provide enough support for the pond to prevent pond collapse by water. It also serves as a walk way to the farmer and farm attendants.
This will help the fish farmer to have an easy look at the pond without supporting the leg with anything and will also make feeding the fishes easy and in addition, it adds beauty to the fish farm.
Importance of Embankment Pond Preparation in Fish Farming
The most important component of the fish farming business is to prepare a pond in a proper way especially the Embankment part. Without the construction of a well-prepared pond, it is not possible to start or run any fish farming business. The importance of pond preparation is given below.
- Aquatic plants and animals which are harmful to fish are controlled
- Cannibalistic and unwanted fishes are removed
- A healthy environment of the pond is preserved
- Optimum pH for fish production is maintained
- Availability of the feed for the cultured fish is ensured
Types of Ponds used in Fish Farming
Within freshwater fish culture unit, different kinds of pond components are used; they are nursery, rearing, production, segregation and breeding/spawning pool.
The percentage of area covered by these different pond types are given below:
Nursery pond: 3%
Rearing pond: 11%
Production pond: 60%
Segregation pond: 1%
Breeding pond: 25%
Nature of Different Ponds
Nursery ponds: Shallow
Rearing ponds: Moderately deep
Production ponds: Moderately deep
Segregation pond: Moderately deep
Breeding ponds: Moderately deep
Water level (for larger production ponds): 2-3 meters
Fish Pond Construction
- Before constructing the pond, land is surveyed to find out determine its topography.
- Marking the area of proposed pond is the first step in the construction of a fish pond.
- The natural slope where the main wall is to be built should be ascertained.
- The main wall should be marked off at the lower end of the pond, where the slope is the greatest.
- The first step while designing fish ponds should be to study the soil type, topography and water supply.
- In designing the fish farm, it should be decided as to where and how many nursery, rearing and stocking ponds are to be constructed.
- In case of a fish farm constructed solely for the purpose of seed production, only nursery and rearing ponds may be constructed, with a nominal area for the brood stock ponds.
- In case of grow-out farm, more stocking ponds will be constructed to produce table size fish after stocking fingerlings.
- For a composite fish farm all three types of ponds are required and their number should be based on the intended stocking density.
- Fish ponds should be at least one surface acre in size. Ponds smaller than one acre seldom support a satisfactory fish population over many years. They usually require much more intensive fish management and may not justify the costs.
- It is important to know the exact size, maximum depth, average depth, and water volume of the pond. This information becomes useful in calculating the amount of herbicide needed for weed control and the number of fish fingerlings needed for stocking.
Preparation of Fish Pond and Fish Pond Embankment
1) Preliminary or preparation stage
Before starting other procedures, the soil should be tested. Samples are collected from the bottom of the pond and dike. Generally, pH and organic matter contents are analyzed. pH is important to determine the amount of lime to be treated later. Soil sampling is very important, especially for the new ponds.
One of the most important steps of pond preparation is to “de-mud” the pond, which we wish to prepare. “De-mud” basically is the process of removing mud from the pond which we wish to use. The main purpose of demudding is to make it more suitable for fish farming.
Demudding can be done just by removing the mud from the pond, which is the easiest way. Instead of demudding directly, we can go for deepening of our pond which is the best option for larger fishes.
The bottom of the pond is dried to remove the unwanted fish species. Drying is done until the soil cracks. Drying also ensures the oxidization of harmful substances and mineralization of organic matters.
Make the dike of the pond taller:
The most common problem of the rainy season for most of the ponds is that flood can carry away fishes of the pond. So, if the pond is located in an area which is closer to the river or stream, then taller embankment or dike is a must. It should be at least 2 to 3 ft higher than the highest level of water in the pond.
This can be done very easily and automatically during the time of digging or demudding. Sand removed during de-mudding/digging can be used to make dikes taller. Otherwise, sandbags can be used to make the dikes/embankments taller.
Efficient inlet and outlet system:
Efficient inlet and outlet system is very much important for the proper working of the pond system. This mostly comes in the form of a pipe through which water can enter and exit from the system. The inlet system of the pond should be placed slightly higher than the outlet system to ensure maximum water flow.
Proper inlet and outlet system prevent overflow of the pond by taking care of heavy rainfall/slight flood. This is very much helpful for the proper maintenance of water quality.
2) Treatment stage
Controlling harmful aquatic plants and animals:
Aquatic weeds and insects both are very much harmful to fish farming ponds as weeds consume almost all nutrients and reduce the amount of oxygen. Their growth should be controlled efficiently so that they cannot create any problem in the pond.
Removing cannibalistic and unwanted fishes:
Removal of cannibalistic and unwanted fishes is very much important step in pond preparation. Shol, gozar, boal, taki, etc. are cannibalistic fish and mola, dhela, chanda, pumpti etc. are unwanted fish.
They can be removed by drying the pond or by using poison in the pond. Rotenone powder is the best option for this purpose.
Conditioning the pond:
Conditioning is done by application of a layer of lime or calcium hydroxide which is spread over the bottom of the pond for two weeks. It is usually applied during or after the pond drying stage. This removes the acidity of the soil, facilitates biogeochemical cycles and prevents unwanted species.
Liming can be done in three different ways:
- By broadcast over a dried pond which includes the dike walls.
- By mixing with water and spraying over the pond and
- By liming the water flowing into the pond.
After 15 days of liming, manuring or fertilization is done in order to facilitate the growth of fish food organisms. Manure can be of organic or chemical nature. The application rate of raw cow dung for stocking pond is 2-3 tons/ha. The application rate of poultry manure is 5000 kg/ha.
Use of chemical fertilizer depends upon the concentration of phosphorus and nitrogen in the soil and varies accordingly. The standard combination of NPK is 18:10:4 for freshwater ponds.
Pond Construction Guide
An intelligent design and layout is a prerequisite for an efficient pond construction. The excavated earth should be used to construct the dyke and with a plodding slope towards the outlet for the proper draining facility. Preferably construction of pond has to be completed during summer so that the pond can be used for stocking.
Steps in Pond Construction
Normally, the pond construction includes the following steps.
Step 1: Prepare the site by removing unwanted things such as the trees, bushes, and rock
Step 2 : Construction of seepage-free and secure dyke by using the clay core
Step 3 : Digging the pond and construction of dyke over the clay core
Step 4 : Inlet and outlet construction
Step 5 : Pond dyke covered with soil and plant grass species (avoid long rooted plants such as Rhodes grass and star grass)
Step 6 : Pond should be fenced to avoid theft and entry of predatory animals
The place is cleared of ropes, cables and other items. Trees and bushes and other obstacles that hinder movement of heavy equipment around the site are to be removed – manually / animal power /using machinery.
All vegetation including wood are to be cleared in the area (inclusive of 2 to 3 m beyond the dyke for workspace). Trees within 10 meters surrounding, tree slumps, large stones, are also to be removed.
The surface soil which has the highest concentration of roots and organic material is not suitable for pond construction. Hence, about 30 cm of surface soil has to be removed.
Construction of dyke
Dykes should be compact, solid and leak free. A desirable dyke is constructed using 15 – 30 percent of silt, 45 – 55 percent of sand and 30 – 35 percent of clay. A sufficient width of the berm (not less than 1 m) is required to stabilize slope.
The embankment slope in horizontal to vertical should be 2:1 in good quality clay soil and 3:1 for loamy silt or sandy soils. To raise the dyke, the clay buddle (1:2 sand and clay) is deposited as 10 – 15 cm thick layer and it can be formed at centre or inside the waterside of the pond.
The crest of the dyke should be sufficient to help allied farm activities and the top of embankment should be above 1 m. Extra outlet is essential on the embankment as a safety measure to avoid damage due to excess raise in the water level.
Digging the pond and construction of dyke
Types of pond
Specific kinds of ponds are required for specific life stage development of fishes – such as nursery, rearing, stocking, treatment and broodstock pond. The rectangular pond is preferred than round shaped corners as it prevents the fish escape during harvest.
An ideal length and breadth ratio of the pond is 3:1 is ideal, with breadth not more than 30 – 50 m. The total farm area can be divided as – nursery – 5 % of total farm area, rearing pond – 20 %, stocking pond – 70 %, and bio pond or treatment pond – 5 % of the total farm area.
- Nursery pond – The size of the nursery pond is about 0.01 to 0.05 ha with a depth of 1.0 – 1.5 m. The spawn (3 days old) are stocked in nursery pond, reared for a maximum of 30 days (to attain 2 – 3 cm length).
- Rearing tank – a tank where the fry are reared into fingerlings (to attain a size of 10 – 15 cm) and the culture duration is 2 – 3 months. The size of pond varies from 0.05 – 0.1 ha with water depth of 1.5 – 2.0 m.
- Stocking pond – In stocking pond, the fingerlings (TL 10 – 15 cm) are reared into marketable size. The culture duration varies from 8 – 10 months. The stocking density varies according to the target fish production. The stocking pond is used as broodstock pond and breeding pond as per the requirement. However, the pond area ranges from 1 – 2 ha with a greater water depth of 2.5 – 3.0 m. There are no hard rules regarding the size of the ponds.
- Bio pond or treatment ponds – these are large settling tanks, where the water used for fishponds is purified biologically. They may also be used as stocking pond. However, an even flat bottom is recommended for easy netting operation.
A productive farm should use its higher altitude area for construction of nursery pond followed by the rearing pond. The lowest area of the farm should be used to build the stocking pond, which will help in reducing the cost of construction and increase ease of farm management.
Pond construction types
The ponds are constructed by two types namely, dug out and embankment pond.
The dug out pond is constructed by digging the soil and is most suitable to construct ponds in plain areas. It is to be scientifically constructed maintaining shape, size, depth and other factors.
Embankment pond is more appropriate for hilly areas. Dykes may be erected on 1 or 2 sides based on need. This pond is economically viable but not ideal for fish culture because the size, shape and depth of pond cannot be fixed as per scientific fish culture specifications.
Inlet and outlet construction
Feeder canals are constructed to provide sufficient amount of quality water to the ponds except in ponds which are filled by rainwater. Inlets are provided at top of the pond and screens are used to filter the pumped water to avoid entry of unwanted particles to the culture system.
The inlet pipe size has to be designed is such a way that it should not take more than 1 or 2 days to fill the pond.
The outlet pipe is set up at bottom of the pond. It is used to dewater the pond during harvest and partial draining for pond water exchange to maintain the water quality of the pond during the culture period. The outlet is constructed prior to pond dyke construction.
Soil and vegetation coverage of Dyke
To reduce the soil erosion, creeping grass can be grown on the top and sides of dyke. The banana and coconut trees can be planted in the embankment.
The slope of the embankment can be planted with grasses such as Hybrid Napier, gunny grass and elephant grass to supply feed to the grass carps reared in the ponds.
The ponds are fenced to protect from theft. Live fences also serve as windbreak, increase farm diversity, provide privacy to farm and improve the appearance of the fish farm. There are several ways to make fences.
These include live fence, piled fence, woven fence, post and rail fence, wire fence, wire netting fence and stone wall. Each type of fence has its own advantages and disadvantages. Wired net fence is primarily used in fish farms to stop intruders and protect the fish stock.
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