Feeding and maintenance in rice-fish system

MAINTENANCE CHECK

Daily check the water level in the field to see that it is not rising or falling unusually quickly. If this occurs, find out what is causing it. Any leaks should be unclogged. A shovel or hoe should be carried on these visits. Some farmers throw a little feed every day in order to monitor their fish stocks. In intensive systems, early morning checks to see if fish are gaping is advisable.

Maintenance check

FEEDING AND FERTILIZING

Feeding and fertilizing should normally help fish grow. However, it is not a major consideration in lightly-stocked fields (below 3000/ha), where fish should be able to forage sufficiently for themselves.

Families who would like to stock more heavily (and therefore to feed and fertilize) need to consider the following points: a) Will they have time to feed or fertilize well? (How far away is the field from their house? What other work do they have to do?) b) Can they get-feed or fertilizer? Is it easily available in the area? Is it affordable?

Feeding and fertilizing

TYPES OF FEED AND FERTILIZER

It is difficult to draw a line between "feed" and "fertilizer," especially since manure can be used as both. Inorganic fertilizers can be used. So can any non-toxic organic material.

Manure is often the most important addition, by weight. Either fresh or dried manure can be used. A little caution with fresh manure may be needed if water is stagnant, but it has been observed that up to 300 kg/ha per week go into such systems without causing harm. Replenishing manure as the fish consume it is another way to cope.

Rice bran is commonly used as a fish feed. It works well in nurseries, but is usually not needed in extensive rice-fish culture. If farmers have to pay for it, they probably should not use much, once fish have entered the field.

Some farmers use rice hulls in their systems and some fish species eat these eagerly. Most of the hull is not digested, but gets spread around the field by the fish.

Kitchen wastes and leftovers of any kind can be given.

Different kinds of water plants work well: Azolla, Wolffia, duckweed (Lemna), pak boong or kangkong (Ipomaea aquatica) and water mimosa are examples. Different fish species will have different preferences but silver barb will eat any of these.

Crop by-products are also acceptable: cabbage leaves and corn cobs have been used by some farmers. Cassava leaves are also popular. Since some-cassava varieties may be poisonous, it is advisable to dry cassava leaves before feeding them to fish.

Termites are a very nutritious feed and are especially helpful in nurseries. Nests are chipped over the pond or field and the termites fall into the water, where they are rapidly consumed. Termites are usually not needed once fish have entered the rice field; if farmers continue to use them heavily throughout the season, they may run out of nests! Other insects, shrimps and worms are similarly nutritious.

Rice straw is not usually eaten directly by fish, but feeds small plants and animals on which fish feed. It can be used anywhere, but may be especially helpful in turbid nursery ponds.

Any otherwise unused dead animals, entrails or body parts can be put to use. In rice fields, they can go directly into the water for fish consumption. In nursery ponds, large, decaying animals can contaminate the pond. Some farmers suspend animal parts over the pond. These attract flies, which lay eggs on the meat; maggots can then be knocked off the meat into the water to feed the fish.

Feed

Jute or kenaf resting can make water temporarily unsuitable for fish culture. The water turns black, oxygen levels drop to near zero and the water smells bad. The resting is very effective, however, in clearing up turbid water. After the resting is finished, pond water quality is often improved. Also, small amounts of jute or kenaf will not harm fish and the rotting material provides feed. Larger amounts can be placed in stagnant water. Good figures for "safe" rates for fish, unfortunately, are not available, so only small amounts should be used and the fish should be checked every morning to see if they are gaping.

Other examples of feeds include mulberry leaves, banana leaves, bat dung, animal feed leftovers, coconut oil residues, Leucaena leaves and livestock dung. No list of potential feed stuffs will be complete.

MANAGEMENT

In densely-stocked fields (over 5000/ha), continuous feeding and fertilizing become important, particularly as the fish grow. Giving small amounts of feed a couple of times a day may be advisable. Check to see how quickly a known amount of vegetation or manure gets consumed. If some amount remain after an hour, there is no need to increase the rate. If it disappears within half an hour, increasing the amount is advisable.

Prepared by: JOHN SOLLOWS

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

The presence of important numbers of predators can affect size and species stocked. Large fish escape predators easily, but this appears a less important consideration for silver barb than for other cultured species.

Culture field characteristics will often affect number and species stocked. Occasionally, silver barb will not grow well in field with very shallow water (less than 10 cm). In small fields, the farmer may find the advisable number of fish limited by available area. On the other hand, there is nothing wrong with stocking few fish in a very large field, especially if this is all the farmer can afford.

.The suggested rate of 3,000/ha can be increased if the field has stable water depth (30 cm or more is preferable) and if the field can be fertilized frequently. If fish are fed, the feed should be put in the field, not in the refuge. Otherwise, they will stay in the refuge, the rice will not benefit and the fish will become overcrowded. Farmers should be very cautious about stocking over 6,000/ha. This can work occasionally, but should be done only by experienced farmers who know their system.

Small fry can be stocked in greater numbers than large fingerlings.

Note: This paper refers to stocking fry and fingerlings, not hatchlings.

If stocking density is low, there is often sufficient natural food in the paddy and no feeding is necessary.

If stocking density is increased, natural food in the paddy is not enough and production is low.

If stocking density is increased, maximum production can still be obtained with supplementary feeding.

Prepared by: JOHN SOLLOWS

FARMER-PROVEN INTEGRATED AGRICULTURE-AQUACULTURE:
A TECHNOLOGY INFORMATION KIT (IlPP-ICLAPM)