a. Water Supply – the site must be accessible to adequate water supply and free from contamination and pollution. Provide each compartment with an individual water inlet and drainage outlet.
b. Soil Characteristics – clay, clay loam, and sandy loam soils are best for fishpond projects. Deposits of organic matter of about 16% are best for fishponds. Avoid sandy, rocky or stony soils because these do not retain water in the pond.
c. Pond Compartments – area of grow-out ponds ranges from 1,000-10,000 sq.m. per compartment, smaller compartments are easier to manage however it requires higher cost for development.
d. Drainage – take into consideration easy drainage to facilitate harvest and proper cleaning of the pond bottom when constructing the pond.
Other factor to consider:
Choose a flat terrain for easier excavation and leveling.
Avoid exposure the fishpond to strong winds which generate wave action that destroys the sides of the dikes.
Construct a diversion canal along the perimeter dike for runoff water during heavy downpour as protection from flood.
Types of Culture System
a. Extensive Culture System – the growth of fish depends on the natural food present in the pond, which is produced through fertilization. No supplemental feeds is given to the fish during the course of the culture period. The recommended stocking density of this kind of culture system is 10,000-20,000 pieces/hectare or 1-2 pcs/sq.m.
b. Semi-Intensive Culture System – the fish depends on the natural food and supplemental feeds. In this system the stocking density is 30,000-50,000 pieces/hectare or 3-5 pieces/sq.m.
c. Intensive Culture System – high stocking density and intensive feeding is required in this type of culture system. Some form of water movement and aeration is necessary to maintain the desired level of dissolved oxygen (DO) in the pond. Water quality monitoring is very important in this system to avoid water pollution that may affect the fish. In fishpond, the stocking density is more than 50,000 pieces/hectare or more than 5 pcs/sq.m.
a. Pond Preparation – the following steps are necessary specially for old ponds:
Total draining of fishpond – to eliminate old stocks, predators and unwanted species such as catfish, mudfish, biya, ayungin.
Pond Poisoning – it is recommended to poison the pond to ensure that all predators and unwanted species are eliminated. If ponds cannot be drained fully, poison is applied by spraying/broadcasting it all over the pond bottom with at least 3-5 cm of water. Recommended poisons are tobacco dust, rotenon (tubli) at 25kg/hectare or a combination of lime and 21-0-0 (5:1), at rate of 3g/liter. Use of chemical pesticides is not advised as it will have residual effect on the pond and will destroy soil quality.
Pond Washing – is done to eliminate the effect of poison be letting filtered water come in and out of the pond.
Leveling/Harrowing of Pond Bottom – the bottom of the pond is leveled to remove excess mud and dirt. It also facilitates harvesting especially during seining.
Sun drying of Pond Bottom – for old ponds, it is recommended to expose the pond bottom to sunlight and allow the soil to crack. Toxic gases evaporate and eliminates faster in a sun dried pond bottom.
Application of Lime – if the pond becomes acidic, application of lime is recommended. The recommended rate is 100g/sq.m. or 1,000kg/ha. Soil samples can be submitted to the BSWM for analysis.
Screening of Water Inlet and Outlet – before filling – in of water, fine mesh screen is installed in the water inlet to avoid entrance of unwanted species and at the water outlet to prevent escape of fish after stocking.
Filling-in of Water – pond is ready to be filled-up with water to the favorable depth of 1-2 meters after screen is installed in the water inlets and outlets.
Basal Fertilization – growth of natural food (plankton) in the pond is produced throudh basal fertilization. Organic fertilizer (chicken manure) is applied through broadcast method all over the pond at a rate of 1,000-2,000 kg/ha. In combination to chicken manure, inorganic fertilizer, 16-20-0 (ammonium phosphate) is also applied at the rate of 100-200 kg/ha by hanging or platform method. This recommended rate may be increased or reduced depending on the amount of natural food is already present in the pond. Basal fertilization should be done one week before stocking. Presence of natural food can be determined through change in color of water into green or yellow green. Over-fertilization should be avoided as it will cause plankton bloom which could result to oxygen depletion. Ammonium phosphate will do if chicken manure is not available.
Stocking of Fingerlings
a. Acclimatization is done to avoid thermals shock that will cause mortalities on the fingerlings. This is done by letting the plastic container float in the pond for 10-20 minutes before releasing the fingerlings.
b. Stocking is usually done early in the morning or late in the afternoon to reduce stress on the stocks. Make sure that fingerlings are acclimatized first before releasing it into the pond.
Pond Care and Maintenance
a. Weed control – growth of weeds such as kangkong and water lily in ponds affects the photosynthetic activity, thereby, reducing production of natural food. Excessive fertilization during pond preparation enhances the growth of aquatic weeds. Some fishpond operators are using grass carp as a means of biological control for weeds.
b. Water management – some important water parameters to be monitored:
Water level/depth – the water should be maintained at 1.2-2.0 meters. For semi-intensive culture management it is advisable to freshen water during the earlier months and change water (30% only) twice a month on the 3rd month and weekly on the last month. Water freshing should be made immediately if problems are observe on the tilapia stocks.
Dissolved oxygen (DO) – low DO level would result to poor growth, disease outbreaks or mortality. Ideal DO level is 5 ppm. This can be maintained by avoiding excessive feeding and stocking.
pH – indicates the hydrogen ion concentration, which determines the acidity or alkalinity of the water. At pH 6.5 to 9.0 fish thrives well and grows fast, below or above this range results to poor growth or mortality. pH level can be determined through laboratory analysis at BFAR.
Temperature – the optimum water temperature favorable to growth of tilapia is 29°C – 31°C. The cold tolerant tilapia however can thrive in temperature as low as 15°C.
Salinity – freshwater tilapia can tolerate salinity up to 5 parts per thousand (ppt), beyond this amount is not desirable. Saline tolerant tilapia can tolerate salinity as high as 15 ppt to 25 ppt, this brees is usually cultured at brackishwater areas.
Turbidity – the presence of suspended solids in the water contributes to the turbidity of water. These suspended solids include sediment particles, silt and organic matters (such as detritus, fecal materials and phytoplanktons). Turbidity can either be harmful or beneficial in tilapia culture. If water turbidity is due to the presence of planktonic organisms (water is green in color), it is beneficial since it serves as food for tilapia and thus enhances growth. But if it is due to suspended silt or other solids, it would only suffocate the fish and will eventually result to mortality of stocks. The ideal level of turbidity is 1,300 mg/l or 25-35 cm visibility using secchi disc, below and above this level is a condition unfavorable for tilapia.
Total ammonia – the un-ionized ammonia is high toxicx to fish. The safe level of un-ionized ammonia is between 0.02 – 0.05 mg/l. Presence of too much ammonia in the pond water exhibits a pungent odor. High ammonia level can be avoided by avoiding overfeeding.
Feeds and Feeding
a. Feeding Methods:
Hand feeding (sabog) – this is done to have same size of fish
Use of feeding bags – feeds are placed in B-nets (32mm mesh size) which are called feeding bags. The bags are tied in poles and they are suspended in pond water surface. Fish obtain feeds in the suspended bags by picking or suction.
b. Determining Average Body Weight (ABW), Daily Feed Ration (DFR) and Feed Convertion Ratio (FCR)
ABW (g) = total weight of fish randomly sampled / # of fish sampled
DFR is the amount of feeds given daily = ABW * total number of stocks * feeding rate * survival rate
TFR is the total amount of feeds given for the whole culture period = DFR * feeding duration
FCR = amount of feeds given during the culture period / weight gain of fish (kgs)