The business of raising Tilapia does not involve growing the fingerlings to marketable size alone. Another profit center in this enterprise that can even be more profitable is the hatchery and nursery operations. The higher profitability of these operations relies on the fact that the feed input is much less than the grow-out operations. Furthermore, in terms of the turn-over rates, the hatchery operations takes only about a week while the nursery operation takes about one month as compared to the four to five months it will take before the marketable sized fish is sold.
Similar to the grow-out culture, the hatchery and nursery of tilapia in tanks offers a solution to increased production at a limited space as compared to the traditional pond and cage culture systems. It also minimizes the risk of crop loss due to typhoons and inundation. Furthermore, intensification of culture means less exploitation of the area and more effective management and controlled operation. It is envisioned that it is only through the tank system that aquaculture can be “industrialized” by providing better control and predictable production levels.
Intensive Hatchery And Nursery Operations
The intensive tank hatchery system uses the incubator technique. Here the eggs are collected from the females’ mouth and are incubated artificially. The advantages of this system are: 1) cannibalism to fry is avoided because the eggs are collected right from the mouth of the female fish, 2) Females re-mature faster, and 3) Increased fry production because the eggs may be treated with anti-bacterial and anti-fungal agents to prevent and control infections.
The components of the intensive tilapia hatchery are as follows:
1. Tank Design:
There is no rule as to the size of the tank to be used for the breeder tank or the nursery tank. However, it is recommended that the tank size should be anywhere from 50 m3 (e.g. 5x10x1.2m) to 100m3. It should be remembered that it is more expensive to construct several small tanks than one big tank.
Both the nursery and breeder tanks should be fitted with aeration and water supply systems for ease in operations. The tanks maybe located indoor or outdoor. It is however preferable to provide shade to prevent large fluctuations in temperature brought about by direct sunlight.
The tanks maybe square, rectangular or circular. Square and rectangular tanks saves space and are cheaper to construct because they share walls as compared to circular tanks. In terms of production performance, there is no difference between a rectangular/square tank and a circular tank.
2. Tilapia Breeder Strain:
It is imperative that good strains of tilapia are used for fast growth. Reputable sources of breeders should be determined for this purpose.
3. Water Supply:
Since tank culture uses a lot of water, adequate supply of good quality water should be available. The amount of water required will depend on the extent of the operation. A shallow well (10-80 ft deep) is suitable because it takes less power to draw out the water. Otherwise, irrigation water or from the tap can be used.
A continuous supply of electric current should be available to operate the basic hatchery facilities such as light, aerators, and small water pumps. When long power failures are expected, a generator set maybe necessary.
The Incubator System
The basic component of the incubator system is as follows:
1. MacDonald Jars/ Fabricated G.I. or Fiberglass egg Incubators.
The capacity of the incubators should range from 2 Ii to a maximum of 20 Ii. Depending on the design and size, an incubator can hold approximately 20,000 eggs/li of water.
The principle in using incubators is to prevent the eggs from stacking together. Thus, water is continuously injected into the system to prevent this from happening.
2. Water Supply
In order to provide continuous water flow at the proper pressure to lift the eggs and prevent them from stacking, a re-circulating water system is employed. This is carried out with the use of an overhead tank.
The overhead tank need not be very high, usually a 6-8 ft height is sufficient. It can be the water storage tank available at hardware or a series of drums of plastic
joined together by a 2” diameter PVC pipe. The bigger the overhead storage tank, the less frequent the water pump will operate.
3. Catch Basin
Usually a cement tank (1 x I x 1 m) or more depending on extent of operation are used to collect the water.
4. Electric Pump
Depending on the extent of the operations, a 0.5 Hp to 2.0 Hp electric pump is used to lift the water from the catch basin to the overhead tank. The pump should be fitted with a float switch located at the overhead tank in order to switch the pump on or off depending on the level of water in the overhead tank The overhead tank should never run out of water for more than 5 minutes because this will cause the eggs in the incubator to stack and die.
Tilapia breeders, that are about 8 months old, are stocked at 20/m3 (15 females: 5males). They are provided with aeration and fed with Tilapia Broodstock Feed at the rate of 1.5-2 % of their Body Weight daily. Feeding is given twice a day, 1/2 in the morning at around 9AM and the other half at around 4 PM. Water quality is maintained by changing 20-50% of the water every 2-3 days or whenever the water becomes turbid.
Harvesting of the eggs and fry is done every 13-14 days as follows:
1. Drain water level up to 15 cm. A hapa net should be fitted at the drainage pipe to
collect the fry.
2. Seine all the breeders. Select the males and place back in the tank
3. Inspect the females with eggs in their mouth and collect eggs by opening the mouth in a basin with little water.
4. Collect all the eggs and place in the incubator.
The tilapia eggs will take around 8 days before all of them develop into fry. Collect all the fry daily inside the incubators by using a scoop net. Place all the fry in the Nursery Tank until they reach the desired fingerling size.
Unlike in the pond system where the nursery has to be prepared by drying, fertilizing, liming, etc. which usually takes more than 2 weeks, the nursery tank only has to be scrubbed-off with algae, filled with water and aerated for about 1 hour. It is then ready for stocking with fry. The time of stocking should still be around 6AM when the water is cooler.
Fry are fed with Fry starter Feed at the rate of 15% of its Body Weight gradually decreasing to 3% for a period of 1 month. Sufficient feed, never in excess, should be given because excessive feeding fouls the water fast. Feeding is generally done 6X daily.
Water management is very important during the nursery operation because it most often lead to the decimation of the stock. Up to 50% of the water should be changed every 2-3 days during the entire operation.