Guide to Proper Fish Pond Construction

A fish pond is a body of standing, as opposed to free-flowing, water that is small enough to be managed for fish culture. Fish production in farm ponds can provide protein and profit for farmers.

Fish such as oreochromis and carp are easy to culture and good yields are possible if a management plan is followed (Figure 1). The three different major operations undertaken in a fish farm includes hatchery and grow out, fish feed production and post-harvest processing.

1. Fish Pond (or Enclosure) Sites: Types

Fish ponds are fish enclosures. They fall into two categories depending on the terrain of the site under construction. These include;

a. Geophore (or Land-Borne) Sites

These are fish pond sites borne by land irrespective of the water source, design and other factors. Earthen ponds, weirs, raceways, fish tanks, through and tubs belong to the category of geophore sites’ enclosure.

b. Aquaphore (or Water-Borne) Sites

These are fish pond sites borne by water (wholly are particularly) irrespective of design and material of construction. Cages, pens, creels, and pots are in this category. They are normally immersed in marine, estuarine, lacustrine and riverine waters.

2. Site Selection

Selection of suitable sites for fish farm construction is very important. The following three essential conditions guide the proper site selection:

• Topography
• Source of water and its quality
• Soil type

a. Topography

It is economical and convenient to construct ponds in waterlogged areas, irrigation command areas or in marginal lands. In such areas construction cost is relatively low mainly due to limited earth cutting.

For example, a pond of 100 m × 40 m (0.4 ha) of water area requires only 3 234 m³ of earth to construct around a dyke of 2 m high above ground level (GL) with side slope ratio of 2:1 and top width of 1.5 m. This quantity of earth may be obtained only from 1.1 m depth of cutting. This limited depth of cutting reduces the construction cost considerably.

However, full consideration should also be given to the possible effects of flood. The surface features of the area proposed for the pond or the farm is also equally important. A saucer-shaped area may be an ideal site for a large dug-out pond, because it may hold appreciable quantity of water with a small amount of earthwork.

For smaller and flat areas eye estimation is enough, but for a big area proposed for farm construction with a number of ponds for different purposes and of different sizes, it is essential to conduct contour survey for determining the topography and land configuration.

The site should be easily approachable so that there may not be any difficulty in the transportation of input materials and in the marketing of the produce. The labour and materials required for construction and operation should also be locally available as far as possible.

From an efficient management point of view the pond site should, if possible, be within the sight of the farmer’s house. It also reduces the risk of poaching. Siting fish ponds near the farmer’s other agricultural or livestock farming activities makes it easier to integrate all the farming activities.

b. Source of Water and Its Quality

A dependable source of water supply must be available within or near the site, even for undrainable ponds. However, unlike drainable ponds, undrainable ponds require just sufficient water to fill the ponds and to compensate the water loss through seepage and surface evaporation thereafter.

Equally important is the need for avoiding excess water and hence there must be arrangement for the excess water to escape through a bypass channel or a spillway.

The water supply to the pond should as far as possible be natural, preferably rain water. However, alternative arrangements of water supply should be made for dry season either from a deep tube well or irrigation canal or from perennial sources like spring, stream, river, etc.

Ponds should be on the lower lands to allow accumulation of surface runoff from a larger catchment area. However, care should be taken to provide proper bypass or spillway to avoid flooding.

A higher subsoil water table due to irrigation in surrounding fields and percolation from artificial or natural channels, in addition to absorption from rain water, also helps in maintaining water level in undrainable ponds.

The quality of the available water is also equally important for fish culture. Pond fish production is influenced by the physical and chemical properties of the water. Water should be clear as far as possible.

Turbid waters which carry suspended solids cut the light penetration, thus reducing primary productivity of the pond. Excess of suspended solids also adhere closely to the gill filaments and cause breathing problems.

Water temperature also significantly influences the feeding and growth of fish. Prevailing water temperature, ranging between 15°C and 35°C in tropical areas, is most suitable for carps. The chemical quality of water depends on its content of dissolved salts. Rain water does not carry any dissolved salts.

However, it collects nutrient salts from the ground surface of the catchment area. The water should be neither be too acid nor too alkaline; neutral or slightly alkaline waters are most suitable for fish culture and hence acid water should be limed to make it neutral. Waters with p^H values below 5.5 or over 8.5 are not proper for fish culture.

The farmer will need huge quantity of lime to neutralize it while highly alkaline water may cause the precipitation of both phosphate and iron, and if it remains continuously above p^H 9, it may be harmful to fish.

c. Soil type

Pond soil must retain water. Soils with a low infiltration rate are most suitable for fish pond. Table 1 shows the filtration rate of different types of soils. The best soils for our purpose are thus the impermeable clay which can be easily compacted and made leak proof.

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Loamy soils can also be used, but they need well compacting, and may leak slightly in the early stages, although they tend to seal themselves with time.

Sandy and gravelly soils should be avoided, but if they are the only ones available they must be made impermeable with a thick coating of clay or with polythene sheeting.

Soil impermeability can also be achieved by soil compaction at the pond bottom and dyke with either a mixture of soil + 1–5% cement or soil + 10–20% cow dung. Treated areas should be kept moist for 2–3 days by gently sprinkling water to avoid cracking and finally the pond is filled with water.

Peat soils have special problems, since they are usually very acidic in nature and need sufficient liming, while the organic matter decomposition may lead to dissolved oxygen deficiency.

Soils rich in limestone also create special problems, since the excessive lime content tends to precipitate phosphate and iron.

Such ponds would then have little plankton population and macrophytes and would be relatively sterile. This can be overcome by adding sufficient organic matter such as cow dung, poultry manure, etc.

A general and convenient field test for the soil quality is to take a handful of moist soil from the test holes made at the proposed site and to compress it into a firm ball. If the ball does not crumble after a little handling, it indicates that it contains sufficient clay for the purpose of pond construction.

Accurate determination of the composition of the soil and its water-holding character is possible by hydrometer method.

Several test holes may be made across the site and soil samples may be collected vertically from every 0.5 m of depth reaching up to a level of 3–4 m in a test hole.

Using the results of the soil tests, a soil profile chart for the proposed site may be drawn. An arbitrary soil profile chart is presented (Fig. 2) showing the presence of clayey soil up to a depth of 3.5 m.

3. Fish Pond Designs

Based upon the survey on topography, soil type, water supply, etc., the detailed designing and layout of the ponds/farm are done. However, the following additional points are also to be considered.

a. Water are a ratio among pond types

The production or stocking ponds are stocked with large size fingerlings of about 10–15 cm size in the case of composite fish culture. To attain this size, the hatchlings are reared in much smaller and shallower ponds called nursery and rearing ponds for about 2–3 months.

In the nursery ponds the hatchlings are reared up to fry stage and in the rearing ponds the fry are reared till fingerling stage. The ratio of water area among nursery, rearing and stocking ponds in a fish farm depend upon the basic objective of the farm.

In case of a fish seed farm, only nursery and rearing ponds are to be constructed with a small area for few stocking ponds to be used for raising the brood fish, while in the case of fish production farm only stocking ponds are to be constructed for producing table size fish from fingerlings.

The layout of a complete farm is given in Figure 3.

There is no hard and fast rule regarding the size of a pond. However, nursery ponds should be small and shallow.

In shallow ponds the water becomes heated easily. In deeper ponds light cannot reach the bottom. In very deep ponds thermal stratification may occur with colder deoxygenated bottom layer.

Dead plankton and faecal matter from fishes may fall on the bottom layer where the nutrients may be locked up.

However, in case of rain-fed areas where the water table goes down during the dry season, the depth should be kept around 3.0 – 3.5 m to store more water during the rainy season.

Although a square pond is economical to construct for its minimum length of dyke, a rectangular shape of the pond (length: width in proportion of 3:1) is considered to be ideal. In any case the pond width should not exceed 30 to 40 m as it is difficult to operate a fishing net in broader ponds.

The nursery and rearing ponds may be square, since they are too small to pose any problem for netting. The corners must be curved to avoid fish escaping the net during harvesting.

The layout plans of nursery, rearing and stocking ponds are given in Figures 4A and 4B.

4. Fish Pond Construction

Before initiating the construction work, proper estimates have to be prepared based upon the design details, which will include the cost of all the materials and the labour. Strict supervision is required at every step of construction to ensure the adherence to specifications laid down in the design.

a. Time of Fish Pond Construction

If the construction work is taken up at the most appropriate time or season of the year, the work becomes easier and economical.

The best time of the year for constructing ponds in clayey soil is post-rainy period and winter when the soil is soft rather than at the end of the dry season when it is very hard.

For swampy and waterlogged areas the most desirable time is the late summer when the area becomes completely dry.

However, if a pond is built during winter or early summer and is not filled immediately, weeds may grow and cover the bottom. In such cases de-weeding is needed before filling the pond.

b. Preparation of Site

The site should be thoroughly cleared of all the trees, bushes, etc. Even the roots of trees should be removed. No woody material should be left because the same will eventually rot and cause leaks. Some tree trunks rot very slowly and may cause problems during netting.

c. Marking the Outlines

This operation involves laying out the features of ponds on the ground in order to mark out the areas from where the earth will have to be cut and removed and also where earth will have to be embanked.

Initially, lines are drawn according to the layout, followed by pegging and fixing stakes or posts. Strings are stretched between the tops of pegs and posts to mark the complete profile of the dyke with its correct height, width and slopes (Fig. 4).

d. Pre-Excavation Work

Prior to pond excavation and dyke construction, all loose surface soil should be removed from about 20 cm depth within the total outlined area of the dyke and the surface should be roughened by ploughing or digging.

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In order to unite the body of the dyke to subsoil, it is desirable to dig a small “V” shaped key trench (Fig.5).

When the dyke is to be made on a sandy, gravelly or marshy soil base, the construction of a key trench becomes essential and in such cases digging should be done until watertight foundations are reached.

The key trench is a small ditch or furrow dug along the line of the centre of the walls about 0.5 m – 1.0 m wide and 0.5 m deep. This trench is filled in with a good clayey soil and is well rammed.

If good clayey soil is not available in the area, ordinary soil should be well compacted into the trench. The purpose of the trench is to stop seepage of water underneath the walls.

e. Pond Excavation and Construction of Dykes

The excavation work can be carried out within the area marked for the pond bottom either manually or mechanically. However, the final levelling of the pond bottom and sides should be done manually with proper ramming and finishing as per the original design.

The construction of the pond becomes economical if earthen dykes are made around the pond using the excavated earth from the pond bed.

All dykes should be raised, dumping the earth layer by layer stretching right across the whole section, and in such cases each layer should not exceed 20 cm in thickness.

All large clods should be broken and each layer should be thoroughly consolidated by watering and ramming. The sides and top of the dykes should be properly dressed and finished with wooden thappies (wooden block with handle for ramming).

In case the soil quality is not suitable for making dykes, a clay core is provided in the dyke to make it watertight. A mixture of 1:2 of sand and clay is used to make the clay puddle. This should be consolidated, compacted and deposited in 10–15 cm thick layers.

Each layer should be adequately moistened before the next layer is laid and precaution should be taken to prevent the puddle from becoming dry and cracking.

Dykes must be well compacted to render them stable and the top should be rammed flat so that small vehicles can also run along when needed. Short creeping grass is recommended to be grown on the top and sides of the dyke. Trees are not desirable since their dense shade inhibits the productivity of the pond.

f. Water In-let Structure

Since we are concerned here with static and undrainable ponds, a feeder stream running directly into the pond should be avoided. The feeder stream must therefore be diverted along the side of the pond and from a suitable point water is channeled to the pond when required.

An inlet structure should be provided through which water can be let into the pond. A proper inlet enables the quantity of water flowing into the pond, to be regulated, preventing the entry of undesirable fish and other aquatic animals and the escape of stocked fish.

For small ponds the best inlet structure is a galvanized iron pipe of about 10 cm diameter with a control tap and a screen basket (Fig. 4 A). The downstream end of the pipe should be 30–40 cm above the water level. A sluice is also suitable for this purpose, especially for larger ponds.

A screen is also fixed to check the entry of undesirable fishes and other animals (Fig. 4 B). To avoid scouring when the pond is being filled, a concrete apron can be built at the sluice, or more cheaply, a layer of gravel lay down.

Similarly, if water is let in with a pipe there should be a gravel bed laid down where the water stream falls into the pond. If gravity feed is not possible, water must be pumped from the supply source into the channel leading to the pond or even directly into the pond; but, in that case, the intake should be securely wrapped by a firm net to prevent undesirable fish and other animals from entering into the pond along with the water.

Function of Some Fish Pond Structures

1. Drainage Installations

Drainage is the disposal of pond water as required by the procedures of fish farm management. Many different draining systems are used, but special mention should be made of the monk and sluice gate.

For clearer terms, a monk is usually associated with fresh water fish pond while sluice gate is associated more with brackish water fish pond.

2. Monk

Monk is known to be the best drainage system and it must be built before the construction of embankment. Monk consists of two main parts namely the shaft and the horizontal pipe. Two or three pair of grooves are incorporated in the shaft, one for the screen, the other two for wood boards.

The monk has two important functions. When the pond is being filled, it controls the level of the water and prevents escape of the fish. When it is being emptied it permits progressive draining of the pond.

3. Sluice Gate

There are two main types of sluice gate notably concrete and wooden sluice gates. Both have the same basic, basic principle of construction, but strong and flexible sluice gate should be fitted to brackish water ponds, despite the fact that the wooden is cheaper to construct. Like the monk sluice gate is located at the lowest point of the pond bed within the dyke base.

Two component parts of the sluice gate are the floor and the twp walls (with grooves for sluice gate boards). Sluice gate is a water control structure associated mostly with brackish water pond. It serves the dual role of letting water in and out of the pond during high and low tides respectively.

4. Water Inlet

Pond water inlet has been amply described by experts as the point or place where water can be let into the pond system.

As an important structure water inlet should functionally assure not only a regular and regulatable supply of water for the system, but prevent both the escape of fish from the pond, and the introduction of unwanted fish into the same pond.

All ponds should be installed with a water inlet structure with the exception of ponds fed by springs with a regular flow.

Fish Pond Factors

1. Factors determining the size of a Fish pond

Cost of construction.

Time required for filling and draining water out of the pond.

Topography of the area may enhance or limit pond size.

2. Factor determining the shape of a Fish pond

Anticipated method of harvesting.

Purpose or function.

Topography.

Ratio between embankment and water body.

3. Types of Fish Ponds based on water supply

There are two major types of ponds based on water supply:

Barrage pond: This type of pond is constructed along the main path of flow of river water or stream. Both up-streams and down streams are barricaded with in-let and out-let respectively

Advantages

It does not cost much to construct. There is usually sufficient amount of water all through the culture period.

Disadvantages

When flood occurs, there is the likelihood that the whole pond system can be washed off.

Diversion or contour pond: This type of pond is constructed in the by-pass of a stream or river. A water supply channel is built for this purpose with a sluice or inlet gate at the entrance to control the volume of water coming in or going out of the pond and also to check on the influx of extraneous materials.

Advantages

It is not prone to any hazard resulting from excessive flooding as compared to barrage type. There is better control over the site contrary to barrage.

Diversion pond is divided into two types:

a. Parallel ponds: Ponds constructed this way are independent of one another in their source of water supply and discharge. All activities relating to filling and draining of water are limited to each pond respectively.

b. Seriesponds: These are built such that each pond derives its water supply from the other and also empties into another. This is the worst approach to pond design hence it is not recommended as whatever affects one would definitely affect the other.

4. Types of Fish Ponds Based on the usage

Holding pond: Used to hold fish temporarily in readiness for either transportation or fattening for induced breeding purpose.

Spawning pond: Used to hold the set of fish intended for artificial propagation

Segregation pond: Used to hold fishes either of the same sex or same species.

Nursery pond: Used to nurse the fry produced during induced breeding into fingerlings.

Grow-out pond: Used to raise fingerlings to table size fish.

Proper Methods of Fish Pond Construction

The actual construction work entails some knowledge of surveying. Surveying which can be described as measurement science is carried out in three dimensions – distance, elevation and direction. In specific terms, the three types of survey of relevant to pond construction are:

1. Coastal survey

This has to do with establishment of some defined boundaries of the proposed land for pond construction with appropriate bench mark.

2. Topograph survey

It is constructed to determine the configuration of the land. This is through measurement of the shape and size of any position or portion of the earth surface and representing same on a reduced scale in map form

In summary, fish ponds are the structural systems designed for fish culture. Their designs vary according to the site of location. Such sites are selected based on the consideration of a variety of factors which determine suitability.

Fish pond sites must be carefully selected to achieve the best production results. A well-selected fish pond site already puts some construction economic in view.

It goes without saying, that fish ponds built on properly selected sites have a better chance of returns on investments, especially when management is adequate.

Fish ponds are enclosure for fish culture, and there are two types based on the terrain of the site under construction: geophore (land-borne) sites and aquaphore (water-borne) sites. Fish pond site selection depends on the nature of the sites: geophore or aquaphore and vary accordingly.

The purpose for which fish pond is being planned will affect the choice of site. This may include fish culture, water-storage, irrigation, hydro-electricity, water storage, flood control, lake resort systems, integrated production (rice-fish, poultry) and vegetable growing.

The actual constructive of ponds entails some knowledge of surveying which could be cadastral survey and topographic survey.

There are two major types of fish ponds based on water supply (barrage and diversion ponds) and five types based on usage (holding ponds, spawning ponds, segregation ponds, nursery ponds and grow-out pond).

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