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Fish Pond Construction and Management, Pond construction:, A pond is a water enclosure or a confined body of water where fish are raised or reared under, a manageable controlled or semi controlled condition. Pond could be either earthen or concrete., Nowadays fish are raised in plastics and wooden rafts which are either locally fabricated or, imported from developed countries., Types of fish ponds:, Within the fish farming pond system there can be different pond components, namely nursery,, rearing, production, segregation and breeding or spawning ponds. The area percentage of these, ponds in a fish-farming complex can be:, Nursery pond, , -, , 3%, , Rearing pond, , -, , 11%, , Production pond -, , 60%, , Segregation pond -, , 1%, , Breeding pond, , 25%, , -, , Nursery ponds are shallow, while the others are moderately deep. In larger production, ponds, water can be maintained at a depth of 2 and 3 metres. A fencing around the fish farm,, may be constructed for protection. Type of ponds according to use are as follows, •, , Spawning ponds for the production of eggs and small fry, , •, , Nursery ponds for the production of larger juveniles, , •, , Brood ponds for brood stock rearing, , •, , Storage ponds for holding fish temporarily, often prior to marketing, , •, , Fattening ponds, for the production of food fish, , •, , Integrated ponds which have crops, animals or other fish ponds around them to supply, waste materials to the pond as feed or fertilizer, , •, , Wintering ponds for holding fish during the cold season., , Site selection for fish pond construction:, The failure or success of fish farm enterprise depends on the selection of a good site. The layout, and the management of fish farm will largely be influenced by the kind of site selected., Land Survey, •, , 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.

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•, , 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., , Designing, •, , 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., , The site has the following influences:, (i) strongly affects the cost of construction, (ii) amount of fish that can be produced, (iii) ease of pond management, (iv) the economics of the enterprise, , Decisions prior to site selection:, ✓ Clear ideal of the type of fish farm which going to to construct, ✓ Of what production level is my target?, ✓ What is the system of culture to be adopted?, ✓ Which fish species should be produced?, ✓ Is it necessary to produce fingerlings for the farm?

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✓ At what stage of fish should you start selling? Answers to these questions will assist, greatly during site selection exercise, , Factors to consider when selecting site for fish farm construction:, ✓ Water- quantity, quality, source, activities around it, ✓ Nature of soil- texture, permeability, retention ability, etc, ✓ Topography of the land, ✓ Environmental consideration, ✓ Accessibility, ✓ Vegetations density/cover, ✓ Biological factors, ✓ Expertise Other important factors include:, ✓ Proximity and size of market, ✓ Poaching, ✓ Availability of farm inputs, Type of Ponds -Three basic pond types, Ponds are grouped into three basic types depending on the way the pond fits in with the, features of the local land topography., Sunken Pond:, 1. The pond floor is below the level of the surrounding land., 2. The pond is directly fed by groundwater or rainfall. It cannot be normally filled by pumping., 3. The sunken pond is undrainable or only partially drainable.

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Barrage Pond:, 1. They are created in the bottom of a valley by building a dam across the lower end of the, valley. They may be built in a series down the valley., 2. The barrage pond is drainable through the old river bed., 3. If large floods are present, the excess water is normally diverted around one side of the pond, to keep the level in the pond constant. A diversion canal is built for this purpose; the pond, water supply is then controlled through a structure called the water intake., 4. Directly fed from a nearby spring, stream or reservoir, the water enters the pond at a point, called the inlet and it flows out at a point called the outlet., 5. To protect the dike from floods, a spill way should be built., , Divergent Pond, 1. The diversion pond is fed indirectly by gravity or by pumping through a diversion canal, from a spring, stream, lake or reservoir. The water flow is controlled through a water, intake. There is an inlet and an outlet for each pond., 2. The diversion pond can be constructed: either on sloping ground as a cut-and-fill pond or, on flat ground as a four-dike embankment pond sometimes called a paddy pond., 3. It is usually drainable through a drainage canal.

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Pond Designing, •, , 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., Construction of pond, After the designing, it is necessary to prepare detailed estimates of the items of work to be, carried out as per the design. The approximate cost of construction is also to be estimated., Construction time, The construction time of the pond is an important factor for pond management. If the, construction of the ponds is completed in summer, the pond can be used for farming, immediately for next season (monsoon)., , Preparation of the site, •, , The site should be cleared before the construction., , •, , All the bushes and small plants, etc. should be cut and removed along with their roots. The, roots should be totally removed; otherwise the leakage problem will arise later on., , •, , If there are any trees near the construction site, it is better to cut the branches overhanging, the ponds, so that the sunlight is not blocked and the leaves do not fall in the water., , •, , It is better to have trees near the ponds, but only 5m away from the pond.

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Mark out the ponds, •, , When the pond area is cleaned, it is necessary to mark the outlines of ponds and dykes., , •, , Mark out the main wall or dyke and other walls with stakes. The walls should be wide., , •, , Plan the depth of the pond and height of walls., , •, , The walls should always be at least 30 cm higher than the water level for a small pond,, and at least 50 cm higher for a larger pond., , Excavation of the pond, •, , It can be carried out either by manual labour or by dozers (JCBs)., , •, , The sides and bottom of ponds should be properly finished and trimmed until a good slope, for drainage is made., , •, , The pond bottom should usually have a slope of 2-5%., , •, , The most important feature is to have the pond bottom slope such that the pond can be, drained., , •, , If the pond site has a natural slope, the dyke or main wall should be constructed at the low, level side., , •, , When the pond walls are constructed, the excavated soil can be placed on the top and planted, with grass., , •, , This fertile top soil will root grass easily and this will help keep the walls from eroding., , •, , The pond bottom must be cleared by removing small rocks, roots, and stumps to prevent the, nets from getting caught and torn during harvesting., , •, , If grass is found in the pond bottom, it need not be removed, because after filling up the pond, with water the grass will die and add nutrients to the water., , •, , When the stakes have been established for construction of dykes, about 2′ top soil should be, removed as it consists of large amounts of roots and other organic material., , •, , The core trench is cut immediately after the removal of the top soil. If the soil is porous, the, seepage problem may arise at a later stage. It would be essential to provide a clay core in, order to prevent seepage., , •, , A soil which is a mixture of sand and clay is best., , •, , Pure clay soil will crack and leak., , •, , If pure clay is to be used, it must be mixed with other soil before it can be used., , •, , Turf, humus or peaty soils should not be used., , •, , All stones, wood pieces and other material which may rot or weaken the wall must be, removed before building begins.

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Construction of dyke, Construction of earthen dyke is always economical. Soil obtained from digging can be used, to prepare the earthen dyke., •, , The filling of earth should be done in layers not exceeding 20 cm in height and consolidate, each layer by watering and ramming., , •, , The earth work for the dykes should be thoroughly compacted so that even minor seepage, can be checked., , •, , If the fish farmer is economically sound, he can go for stone pitched dykes., , •, , The dykes of a pond should be strong enough to withstand weather action., , •, , In big ponds, erosion of dykes is a problem which requires regular attention., , •, , Brick or stone pitching may be provided to arrest erosion of dykes., , •, , Earthen dykes can be protected from erosions with bamboo piling., , •, , Holes should be closed immediately with stiff clay mixed with lime and cementing material, and should be compacted properly., , •, , By using concrete blocks, stones or bricks the earthen dykes will be protected more, permanently from crab or rat holes., , •, , Side slopes of embankments depend upon the nature of material used for construction. The, slopes should be flatter than the angle., , •, , Soil with a lot of clay in it can have a greater slope on the outside wall than on the inside, wall., , •, , A typical embankment is built with an outside slope of 1:1 and an inside slope of 1:2., , •, , A slope of 1:2 means that for every increase in 2m width there is a change of 1 m in height., , •, , Once the embankment is constructed, it is better to plant grass on it., , •, , The grass roots help to hold the wall together and prevent erosion of the soil., , Structure Dyke

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Construction of dyke, , Drainage system, A drainage system is used to empty the pond. It consists of the outlet system for letting water, out of the pond and the drainage ditches which carry the water away from the pond., •, , The best and easiest way to have a good drainage system is to build the pond in a place which, provides a good slope., , •, , The drainage system must be built before the pond embankment because some drainage, devices go through the walls., , •, , One of the easiest ways to drain the pond is to place a bamboo or plastic pipe through the, base of the wall into the middle of the pond., , •, , The end of the pipe, which is inside the pond, should have a screen over it to keep fish from, entering the pipe. The other end of the pipe is plugged with wood or clay. To drain the pond, during harvest time, the plug is pulled out., , •, , Other methods of draining the ponds are the siphon and the pump.

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Drainage of the pond, Sluice, •, , The sluice can be a screened gate in a water channel going into the pond or drainage, , gate leading water out of the pond., •, , The sluice can be made of wood, cement and brick. It can be made up of one or two wooden, gates which are removed to empty or fill the pond., , •, , A sluice also has a screen gate to keep unwanted fish from entering at the inlet and pond fish, from leaving at the outlet., , Water inlet, •, , All the ponds, except for those filled directly by a spring or by rainwater, need water inlets., , •, , During the construction of inlets, filters should be used in the channel so that the unwanted, fish or other materials do not enter into the pond and the water is clean., , •, , A water inlet can be as simple as a bamboo pipe of good diameter running from a water, source through the wall into the pond., , •, , The inlet pipe should be placed above the water level., , •, , A wire screen makes a good filter., , •, , The horizontal screen is very effective., , •, , A nylon mesh bag makes a good filter and can be fixed to the inlet pipe., , •, , A sand and gravel filter is also used, but it requires a small tank at the water inlet, it is more, effective and economical., , •, , If the water is muddy, or has plenty of leaves or grass in it, the wire screen is better., , •, , If the water source is free from organic material, the mesh bag will work., , •, , If the water contains unwanted fish and more organic matter, sand and gravel filters are best.

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Sealing the pond bottom, Leaking Ponds, One of the most common farm pond problems is heavy water loss through leakage. The, ability of the pond to retain water depends largely on the characteristics of the soil at the pond, site. Most leaky pond problems can and should be prevented by cautious site selection. Before, building a pond, be sure to test the capacity of the soil to hold water. Soils with a high clay, content will minimize seepage since clay particles tend to swell when wet and, thereby,, provide a good bottom seal., •, , If the soil has more clay in it, no special sealing is needed., , •, , If the bottom is sandy, it should be sealed to hold the water. To seal the bottom a clay core, lining is built over the pond bottom., , •, , Another method of sealing the pond bottom is with cement blocks, but it is expensive., , •, , The most commonly used pond sealant is bentonite clay. Bentonite is most effective on sandy, soils that contain insufficient amounts of clay. For best results, bentonite should be spread, evenly over the dry pond bottom at a rate of 50 lbs/100 ft (20,000 lbs/acre) mixed with the, existing soil, moistened, and then compacted with a roller., , •, , Sealing with flexible plastic sheeting of polyethylene, or plastic or vinyl, or butyl or rubber, sheet liner at least 2 mm thick is another method of sealing., , •, , The pond liners should be covered by at least 6 inches of sand or fine soil., , •, , Technique developed in the USSR, is called gley or biological plastic. In this method, the, pond bottom is covered with animal manure after cleaning the bottom. The animal manure, layer is then covered with banana leaves, cut grasses or any vegetable matter, and a layer of, soil is put on it. The layers are rammed down very well and 2-3 weeks are allowed to elapse, before filling the pond.