DEPARTMENT OF LIVESTOCK - FAO / UNDP PROJECT
LAO / 78 / 014
VIENTIANE NOVEMBER, 1983
HOW TO CULTURE PA NIN IN PONDS
Pa nin (Tilapia nilotica) is a good fish for culture. It breeds in ponds and feeds voraciously on most of the natural food (plankton, bottom biota, vegetation etc.) present in ponds prefers vegetable food; it grows fast and its meat is tasty.
Pa nin may appear to be an easy fish for culture, but not so. It needs good care, if you want good growth of fish and high production. Normally, pa nin starts breeding even when 3 months old at a size of about 8 cm onwards. Within a few months of culture, the pond gets full with small fishes and later due to overpopulation, the growth of fish is slow and the fish farmer gets very little or no profit.
To produce a good crop, quality seed of pa nin is required. So it is important to select good, large, healthy male and female brood fish for the purpose. The male fish grows faster and is larger in size than the female. The adult male is more brightly coloured than the female ( Fig. 1 ). However, a male can easily be distinguished from the female by its more prominent urino-genital papilla - a finger-like structure situated below the anus. The male has only one urino-genital opening at the tip of the papilla whereas, the female possesses two openings-the one in the centre is the genital pore through which eggs are released while the terminal one is urinary opening ( Fig. 2 ). The male fish makes saucershaped nests on the pond bottom wherein the female fish lays eggs. The eggs are immediately fertilized by the male and the female picks up the fertilized eggs in her mouth where the eggs hatch out. A female may lay eggs at an interval of 1½ to 2 months at suitable water temperatures.
Method of Pa Nin Culture
When you start pa nin culture, make sure that you are growing pa nin (Tilapia nilotica) and not the inferior species pa mothet (Tilapia mossambica). So it is important to know the main differences between the two species. To distinguish pa nin from pa mothet just examine the tail of each species. Pa nin is easily distinguished by the vertical white stripes in the caudal fin ( tail ), which are absent in pa mothet ( Fig. 3 ).
For pa nin culture, preferably select small - sized seasonal ponds or those ponds which cannot be used for culture of big fishes like Asiatic carps, etc. In case larger perennial ponds are used for pa nin culture, all the fishes already present in the pond may be removed by dewatering, thorough netting or using any suitable fish poison.
Put lime in the pond at the rate of 200 kg / ha.
One week after lime application, apply fresh pig or cowdung (at the rate of 5,000 kg/ha) or poultry droppings (at 300 kg/ha) initially.
Two weeks after manuring, stock the ponds with small pa nin, at the rate of 15,000–20,000 fry (20–25mm) or 8,000–10,000 fingerlings (35–40mm) per hectare.
After about 2 to 3 months of culture, when pa nin grow quite big, stock pa thong (Notopterus chitala) at the rate of 100–200/ha (average weight 60–100g) in the pond. Pa thong, a minor predator, will control the population of pa nin by eating the small pa nin produced as a result of natural breeding. Pa thong which has a big body but a small mouth checks overpopulation of small pa nin in the pond. The fry which escape predation grow faster and reach the marketable size (Fig. 4). However, when pa thong is not available, the overpopulation of small panin can be kept under check by regular netting and removal of small-sized fish. These fry, early fingerlings could be sold to other farmers. If small size pa nin are not removed regularly, the pond will soon get overpopulated and the fry will get stunted resulting in poor production (Fig. 5).
Regularly harvest the large market-size pa nin (about 100–150g) and replace number by fingerlings, thus maintaining about 8,000–10,000 pa nin fingerlings / ha in the pond. However, go on manuring the pond at regular intervals and feeding the fish with your kitchen and garden refuse and locally available cheap feed like rice bran, oil-cake, etc.
If you can construct a poultry shed or pigsty hanging over the water surface from pond margin, you can save money and effort to a considerable extent in manuring the pond and feeding pa nin, thus integrate pa nin-cum-poultry/pig culture for your homestead pond.
You will be happy to harvest from your pond a regular crop of large tasty pa nin a high quality protein to eat and a good income by selling the surplus fish.