Stocking for rice-fish culture

The following guidelines apply in any case where seed fish are transported and stocked:

· Transport and stocking are best done early in the morning or failing this, late in the day when temperatures are lower.

· Fish, once purchased, should be transported promptly and kept out of direct sunlight.

· They should not be shaken up, or unduly disturbed.

· On arrival at the pond or ricefield, bags should be set in the water (where the fish will be released) for several minutes until temperatures become the same in and outside the bags.

· Bags should only then be opened and fish should be immediately allowed to swim into their new home of their own accord.

Transport and stocking are best done early in the morning

TIMING

The earlier in the season that fish can be stocked, the longer the growing period. Also, the earlier in the rainy season, the fewer the predators.

On the other hand, fish cannot be stocked before there is water available and the farmer should be reasonably sure that the field will hold water for several months before he stocks. Rice should also be well established with 2-3 tillers out before fingerlings or large fish are allowed into the field.

Finally, the farmer may be ready to stock, but seed fish may not be available. Therefore, the family may have to wait until fish can be found.

STOCKING RATES, SITES AND SPECIES

There is no best" formula here. Large fish are more expensive than small ones, but are better able to escape peration. Species can differ in price. Many fish cost more than few; the family's budget, then, can affect what is stocked.

Stocking rates

For beginning farmers, and for those who cannot feed their fish, stocking not more than 300 (5 cm) fish per 1000 sq m is suggested. A species ratio that commonly works in Thailand is common carp (Cyprlus carplo), silver barb (Puntius gonlonotus) and tilapia (Oreochromis alloticus).

This formula will not be appropriate in every case, but is as good a point of beginning as any. In general, H is better to culture two or more species than only one, sine-e different kinds of fish eat different foods. This means total catch should be higher than if only one species is raised. The formula given can be modified for many reasons:

1 Availability: A farmer may want a certain A combination of species and sizes but still have to be content with what she can find on the market.

Combination of species

2. Preference: Each family will have different species preferences, usually for valid reasons. These should be accepted. Similarly, many farmers prefer large seed because of their higher survival or greater final size. Others prefer small seed—despite probable higher mortalities — because of lower prices and higher continuity of harvesting; specific prices will affect the economics here. The family with limited budget must often decide between buying a few large fish or many small ones.

3. Species-specific biology

Fish species have differing advantages and disadvantages: Tilapia (Oreochromis niloticus tolerates environmental extremes very well and reproduces easily. The farmers who can keep a few fish all year around need not worry about restocking every year. However, reproduction can lead to overcrowding and poor growth. Some farmers do not like the taste, find it ferments poorly and complain that it competes with or drives away other desirable species.

Common carp (Cyprinus carpio) tolerates poor water quality and shows excellent growth in most rice fields. Poor survival, probably due to high susceptibility to predation.

Sliver barb (Puntius gonlonotus) usually has excellent survival in rice fields: even fry tend to show good recovery. it is less tolerant of poor water quality than the other two species above and does not grow well in very shallow water or water of highly unstable depth.

Various wild species, notably snakehead (Channa sp.) and walking catfish (C/arias sp.) are very palatable.

The snakeskin gouraml (Trichogaster pectoralls) has shown very promising results in a few rainfed ricefields. Broodfish, not seed, should be stocked. More work should be done on this species under rainfed conditions.

Chinese and Indian major carp usually show poor growth in rainfed fields. in deeper water (50 cm or higher), they appear to do better. They should be stocked at low rates, no more than 200/ha.

6. Since this is a subsistence activity, to a large extent, there is little competition on the market armory producers.

7. Rice yields are usually enhanced, although there is great variation from farm to farm. Yields are very rarely adversely affected when the farmer manages the system well.

8. The fact that this technology can modestly Improve the lives of many poor rice farmers should make it of interest to development workers.

Prepared by: JOHN SOLLOWS

FARMER-PROVEN INTEGRATED AGRICULTURE- AQUACULTURE:
A TECHNOLOGY INFORMATION KIT (IIRR- ICLARM)