|By pinoyfarmer | March 13, 2010|
Site Selection and Engineering
The success of freshwater fishpond farming depends on the selection of ideal fishpon site, proper planning and layout design, proper construction and appropriate pond management.
Considering the expenses involved in pond construction, freshwater fishponds smaller than half a hectare are not commercially viable. This technoguide is designed for freshwater fishponds with an area of one-half hectare or more.
Water supply. Water supply is the foremost factor to consider in selecting a fishpond site. The site must be accessible to adequate water supply throughout the year and free from pesticide contamination and pollution. Sources of water can be a surface runoff, stream, creek or irrigation.
Soil characteristics. Clay, clay loam, and sandy loam soils with deposits of organic matter of about 16% are best for fishponds. Hard mud of the above types are preferable to the soft and very loose kind. Avoid sandy, rocky or stony soils because these do not retain water in the ponds. Some of the methods to determine if the soil will hold water are:
- Squeeze a handful of wet soil. Its shape is retained when the grip is released.
- Make a soil ball. It will not crumble into pieces if thrown into the air.
Avoid areas with thick deposits of organic debris since these are poor materials for diking. Consider also the pH value of the soil in selecting the site. The most desirable range of pH is 7-9.
Topography. Choose flat terrains for easier excavation and levelling. If the topography is to undulating, the construction costs increase greatly and excavation work removes the fertile portion of the pond bottom. Avoid sites that are frequently flooded.
Other factors to consider are availability of quality fingerlings and cheap skilled labor, accessibility to market and peace and order condition.
Designing and Planning the Layout
In designing and planning the layout of freshwater fishponds, give careful consideration to the following:
Pond compartments. There are three compartments in a complete freshwater fishpond system namely: nursery pond, brood pond and production or rearing pond. The nursery and brood pons may comprise 10% of the total area, and 90% for the production pond.
The pond may be rectangular or irregular in shape. The size of the compartment is governed by the topography of the land. This may vary from less than one to two hectares for good management. Smaller pond units require greater construction and maintenance cost.
Water supply. Provide each compartment with an individual water supply system and drainage outlet. Provide also a mechanical emergency spillway for the flow of excess water from ordinary rain and to maintain desired water level in the pond.
Drainage. Construct the pond to facilitate easy drainage when harvesting fish stock and proper cleaning of the pond bottom.
Elevation. Construct the pond one meter or more lower than the source of water supply but slightly higher than the drainage area to obtain at least an average water depth of one meter for maximum production.
Wind direction. Wind plays a role in fishpond design. Strong wind generates wave action that destroys the sides of the dikes. To minimize this, position the longer pond dimensions parallel to the direction of the prevailing wind to lessen the side length of the dike exposed to wave action.
Protection from flood. If the fish pond site is prone to flooding, construct a diversion canal along the perimeter dike to divert runoff water during heavy downpour. Construct a larger and higher perimeter dike to prevent inflow of water.
Designing dikes. Construct dikes with trapezoidal cross section with the top width, the side slopes and the height proportionally designed according to the soil material used. The following are guidelines in designing the dikes:
- Height above water line. Extend the top of the dike sufficiently above the water line to give a safe margin against overtopping during flood. Include margin for wave action caused by exposure to winds. Perimeter dike should have, after shrinkage, a freeboard height of 0.60 – 1.0 m above the maximum level observed in the locality. Freeboard for secondary dikes is 50 cm. The allowance for settlement and shrinkage depends on the characteristics of soil fill, soil foundation, and on the method of construction. On the average, an allowance for settlement and shrinkage is 25%. Provide a settlement allowance of not less than 40% for soils high in organic matter while dikes compacted by construction equipment is 5% less than the filled height.
- Top width. The minimum top width or crown is 1 m for dikes less than 3 m high. The top width of dikes used as access road is 4 m. Provide a 0.60 m wide berm or shoulder on each side of a roadway dike to prevent rovelling.
- Side Slope. The side slope or steepness of the dike is the ratio of the horizontal length to the vertical rise. Fishpond dikes lower than 3 m should have a slope of 1:1. Dikes above 3 m should adopt a 2:1 slope. Refer to the table below for relationship among the top width, bottom width and height of dikes.
|Height||Top width of crown (m)||Bottom, with in m. at given side slope|
|1:1 ratio||1.5:1 ratio||2:1 ratio|
Preparation of Program of Work and Schedule of Development
Project programming is undertaken to determine how and when a project will start and be completed within a given period based on daily output, or by determining the number of days a piece of work can be finished based on the available labor in the area.
The program of work is the basis of implementation of the project. Evaluate and calculate each item realistically so that each job is properly developed and economically done.
|Activities||Nature of work||Daily Labor|
|Support facilities & equipment|
|Clearing/marking & levelling of dikes||daily||5 laborers||14||plastic hose (1 cm diameter, 50 cm long), meter stick|
a. construction of dikes
b. construction of canals
|digging blades, tractor, rotavator|
|Construction & installation of gates & pipes|
|Finishing touches||daily||5 laborers||10||-|
Construction of Pond System
Plan fishpond construction carefully and systematically. The system of pond constructioin is based on the prepared program and schedul of development.
Schedule of Development
|1. Clearing/marking path &|
a. Construction of dikes
b. Construction of canals
|3. Construction and installation of gates and pipes|
|4. Finishing touches||————–|
Clearing the area. Clear the entire area of all grasses, roots and stumps. Burn these thoroughly. Strip surface to an adequate depth to remove all objectionable or organic matters.
Dike construction. Clear the dike site of vegetation, slumps and debris. Clear the strip 2-4 m wider than the base of the dike. For sites with decaying matters, construct a puddle trench at the center of the path of the dike. Excavate 0.5 m wide by 0.5 m deep trench filled with clay soil to prevent excessive seepage on the finished dike. Dig blocks of mud for construction of dike at least one meter from its base. Allow each layer to settle firmly before adding another layer until the desired height is attained. Construct dikes either manually, mechanicaly or both.
It is very important to have a uniform dike height. To do this, get a 50 m long transparent plastic hose. Fill the hose with water. Hold one end of the hose at the first station and the other end at the next 40 m away (figure 6). If the water level at both ends are the same, the dike is level. Repeat the process until the last station has been marked.
Canal construction. Construct the canals simultaneously as the adjacent dikes. Stake markers to serve as guide during the excavation of canals. Slope the canal gently towards the drainage gate of pipe to keep the flow of water sluggish and to avoid excessive erosion.
Construction and Installation of Water Control Structures
Water inlet or outlet structures are usually made of wood or concrete gates, galvanized iron sheets or reinforced concrete pipes.
Place 3 pairs of grooves on each side of wooden or concrete gates extending to the top of the dike where they are installed. The middle pair of grooves allows the removable slabs to regulate the flow of water. The first and third pairs enable the screens to prevent the escape of cultured fish. These screens may either be of bamboo splits or nylon attached to a wooden frame.
In freshwater fishponds, galvanized iron pipes or reinforced concrete pipes are often used instead of concrete wooden gates. The following is a guide in determining the proper pipe diameter to be installed.
|Size of drain pipe in inches||Condition|
|Can drain 1 ha. pond with average depth of 1 m in 6 days|
Can drain the same in three days
Can drain the same in one day
Source: Site Selection, Design/Layout and Construction of Fishpond by C.R. dela Cruz
With proper scheduling of draining time, it is adequate to use 4 to 6 inch pipe for one hectare pond and 6 to 11 inch pipe for larger ponds.
Construct water supply and drainage system simultaneously with the dikes.
Pond bottom levelling
Mechanical levelling is cheaper and faster than manual levelling if the pond bottom can support the equipment used. Use farm tractors or tillers with a back blade. The carabao and the harrow may be used in small ponds. The pond bottom should slope gently towards the drainage gate to facilitate complete drainage.
After levelling the pond, plant creeping grasses at the dikes to prevent erosion. Plant bananas at the outside slope of the perimeter dike to serve as wind breakers. Do not plant trees along the dikes because the roots will cause leakage and seepage.
Management of Freshwater Fishponds
Prepare the ponds a month before stocking fish in the following manner:
Draining and drying. Drain and dry the pond completely. Dry for about a week or more, depending upon the weather, until the bottom cracks or harden sufficiently to support a man on his feet without sinking more than 1 cm.
Make sure the pond soil is dried everytime the pond is harvested.Periodic drying stabilize soil colloids and oxidizes organic matters that encourage the growth of natural fish foods. Draining and drying eradicate competitor fishes and predators, and kill disease-causing organisms.
Cultivation of pond bottom. Till or cultivate the pond bottom as soon as it is drained. Do this by stirring or cultivating with a shovel or a rake for small ponds. For large pons, use a rotavator.
Cultivation makes sub-surface nutrients available at the surface for the growth of fish food in the pond, eradicate burrowing predators like mudfish and eliminate undesirable pond weeds like “aragan.”
Levelling. Level the pond bottom after this is cultivated. Levelling makes the pond bottom slope gradually from its farthest end down towards the drainage structures – the deepest portion of the pond.
Repairing gates and screens. Check all gates and pipes for broken slabs and other parts. Repair screens to prevent predators and pests from entering the pond system. Clean to remove debris which may cause clogging.
Repairing dikes. Check all dikes for leakages and seepages. All dikes must be water-tight. Put a puddle trench excavated about 30 cm wide and 50 cm deep or more along the dike. Build this at the center of dike towards one side, or dig two puddle trenches at both sides of pubbled trench long enough to cover the entire seepage and sufficiently deep to go beyond the general level of the pond floor. Fill the trench with new mud or soil. Allow the soil to settle well to give a firm line of earth.
Pests, Competition and Predator Control
Fish production in ponds is commonly affected by some pests and predators. Predators are organisms which prey on the cultured fish. Animals that compete for food or space are called competitors.
a. Piscivorous or predatory fish and other competitors
Catfish (hito), mudfish (dalag) and gourami may enter ponds during floods or when accidentally stocked with the cultured fish. These predators devour fry and fingerlings during or after stocking. To avoid them, drain the pond totally after harvest or before stocking.
Mudfish which tends to burrow into the mud, can be totally eliminated by using tobacco dust at the rate of 500 kg/ha.
Screen water gates and outlets properly to prevent entry of unwanted fishes. Check fingerlings properly for any possible contamination by predatory fish prior to stocking. Competitors are associated with predators. Both compete with the stocked fish for space and food.
Herons, kingfishers and other birds must be prevented from frequenting the ponds. They devour fish and fingerlings and are also carriers of parasites. Ponds constructed without shallow areas are not attractive to birds.
Snakes prey on small fish. Always keep banks and dikes clean to prevent snakes from harboring in the ponds.
Frogs eat fry and fingerlings. Tadpoles also compete with the fish for space and oxygen. Frogs are seldom found in well-fertilized and well-stocked ponds. Their population can be controlled by removing their egg sacks from the pond water.
Soil acidity limits the production of natural fish food by decreasing the amount of plant nutrients and, in some extreme cases, kill fish. In cases where soil pH is below 7.0, it is important to control acidity to ensure high fish production.
Analyze pond soil at least once a year to determine its exact pH value. Soil analysis is especially recommended for newly constructed fishponds as basis for proper soil conditioning. Refer to Appendix D for proper collection of soil sample.
Methods of controlling and correcting acidity
- Leaching. Wash or flush the pond bottom to reduce acidity. This process is effective in slightly acidic soil.
- Liming. Apply lime in fishponds primarily as a soil conditioner. Liming corrects soil acidity, promotes the release of soil nutrients, precipitates suspended materials which hamper light penetration and reduces incidence of fish diseases.Agricultural lime (CaCO3) is the most common time used in fishponds. Unslaked lime or quicklime (CaO) and slaked lime (Ca COH)2 or hydrated lime may also be applied. These are available on arrangement with agricultural input dealers.
Procedure in lime application
Broadcast or spread the needed lime over the drained but moist pond bottom. Mix the lime, thoroughly with the soil to attain maximum effectiveness. Allow one week to lapse before applying phosphate fertilizer.
Applying fertilizer in ponds to supply the nutrients needed for plant growth is a fundamental part of fishpond management. Fish production per unit area can be increased as much as five-fold by proper application of fertilizer. Fertilizers are classified into two groups:
Organic Fertilizer. The nutrients and organic matter content of manure increase the water holding capacity of the soil, decrease the rate of evaporation and increase enzymatic activity, all of which increase fertility and yield. Animal manures contain the major nutrient components such as nitrogen (N), phosphorous (P), and potassium (K), in addition to such trace elements as calcium (Ca), copper Cu) iron (Fe) and magnesium (Mg). Phosphorous comes mainly from feces except from swine manure which has more nitrogen and potassium. Animals fed with roughage ration excrete more potassium than those fed with high concentrate rations.
The chemical composition of manure also varies depending upon the animals, nature and amount of manure and the handling and storage of the manure before use. The most common organic fertilizer used in fishponds are chicken dung, cattle manure and swine manure. Chicken manure may be utilized as fish feeds and at the same time helps create a soft mulch bottom to make a habitat for other food organisms. Compost, rice bran, and sewage may also be used.
Inorganic Fertilizer. These are chemical fertilizers containing concentrated amount of at least one of the three major plant nutrients: nitrogen, phosphorous, and potassium. The common fertilizers used in fishponds are Super phosphate (0-20-0), Monoammonium phosphate (16-20-0), and Diammonium phosphate (18-45-0).
Techniques in Fertilizer Application
- Apply animal manure in heaps of 20-50 kg at several locations in the pond to prevent excessive absorption of dissolved oxygen during decomposition.
- Apply inorganic fertilizers in fishponds using the platform method. The platform is a tablelike structure about 75 sq m positioned with its surface horizontal beneath the water surface. Bamboos are excellent for constructing platforms (Figure 7).Position the platform 15-20 cm below the water surface. Do not place this in corner, or in areas shielded from the wind. The platform saves approximately 20-40% of the required amount of fertilizer.
- Put the inorganic fertilizers by placing them in gunny sacks suspended in the water to enable this fertilizer to dissolve gradually thus, providing a continuous supply of nutrients for the plankton.
Plankton is a collective term for all the small suspended organisms that passively drift and float in the water. Most planktonic organisms are microscopic and consist of phytoplankton (very small plants) and zooplankton (very small animals).
Tilapia consumes plankton as food. Plankton is responsible for producing greater fish weight than any other type of natural food raised in ponds.
Procedure in Growing Plankton:
- Drain the water completely for a minimum of 24 hours.
- Fill the pond with water to an average depth of at least 20-40 cm. Increase water level to 80 cm after the first week.
- Apply 22 kg/ha of 18-45-0 or kg of 16-20-0 per hectare on the platform.
- In case of organic fertilizer (chicken, hog, cow or carabao manure), apply 1.5-2 tons per hectare of pond per month.
- Stock the pond after one week.
- Repeat the same fertilizer treatment after one week and then as often as necessary to keep visibility to 30-40 cm.
Source: Department of Agriculture – Philippines