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close this bookWorkshop to Produce an Information Kit on Farmer-proven. Integrated Agriculture-aquaculture Technologies (IIRR, 1992, 119 p.)
close this folderManagement for rice-fish
View the document(introduction...)
View the documentSite selection: where to culture fish with rice'
View the documentPreparation of field for Rich - fish culture
View the documentStocking for rice-fish culture
View the documentFeeding and maintenance in rice-fish system
View the documentRice management in rice-fish culture
View the documentRice-fish benefits and problems
View the documentThe rice-fish ecosystem
View the documentFish as a component of integrated pest management (ipm) in rice production

(introduction...)


Site selection: where to culture fish with rice'

1. Does the family have a particular area in mind? Whatever the answer, try to visit either the specific plot or the general area with one or more family members.


Site selection

2. If the family already has an area in mind, ask what they like about the area and take these into account in considering the following points.

3. Water (most important)

The field must hold water continuously for several months; the longer, the better, from the point of view of the fish. For best results, the field should be covered to a depth of about 30 cm, but if some areas are shallower or deeper than this, there is no serious problem.

Does the farmer think he can achieve this? The higher-lying the field, the less water it is likely to catch. However, dikes and field boundaries must be above maximum flood level. The lower-lying the field, the more flood-prone it becomes. At what level does the farmer feel sure he can control flooding?


Water (A)


Water (B)

4. Clay will hold water better than sand. Where does the farmer feel water will stand longest?

If the field must be placed on a sandy area, generous manuring throughout the season will improve its waterholding capacity. How much manure can the farmer add?

Form a compact ball from a handful of soil and drop it half a meter to your other hand. If the ball does not break, the soil holds water well. Successful culture is possible in poor soils, but faces more limitations.

5. How close to the farmer's house or "working shelter" can the field be placed? This makes checking the ricefield and feeding the fish less time-consuming. It also helps to discourage thieves.

6. Preparing the ricefield for fish culture is a lot of work. How can the farmer take advantage of existing conditions on his land to save manpower? Some examples are given below:

· A small knoll or termite nest can help provide part of the boundary for the field. This will reduce the length of the dike needed around the field.

· If the land slopes, a high dike on the uphill side at the field is usually not needed. The lay of the land will help confine the fish.

· Does the farmer have a pond within the richfield already? If he can include the pond in his system, he may no longer need to dig a trench or pond.

· If the ricefield is basin-shaped, this can rave a lot of work. The middle of the field is the deepest point and little effort should be needed to raise dikes.

7. Is there any chance poisonous chemicals (industrial wastes, pesticides, etc.) will run into the field? Try to make sure this doesn't happen, since these poisons may kill all the fish.

8. The earlier a field is transplanted, the sooner it will be ready for fish. This means the fish may have a longer growing period.

9. The farmer may want to integrate his fish culture operation with his livestock, vegetable garden or other operations. In such a case, the site he selects may not be best for fish, but may be good for the whole operation.

10. Can the placement of the pond cause neighboring fields any problem?


The placement of the pond cause neighboring fields any problem

11. Any other considerations? Ask the farmer!

Prepared by:JOHN SOLLOWS

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

Preparation of field for Rich - fish culture

Good preparation is very important in order to succeed in rice-fish culture. Every farmer must be able to:

hold enough water over a large enough area for enough time to produce enough fish; and, prevent serious flooding of the dikes and other boundaries of his rice field.

Having a satisfactory water situation in the field is a key factor in the technology; this cannot be achieved if preparation is poor. In field preparation, there are four main things to consider: field size and shape, dikes refuges and drains.

Field size and shape

1. How much land does the farmer own? If the farmer does not own the land and the landlord is agreeable, how big an area does the landlord want to try?


Field size and shape

2. Topography and slope will greatly affect field size and shape. It may be possible to construct a large square field on very flat land, but not quite so in sloping areas.

3. What area does the farmer think is suitable? This can limit field size and affect field shape. (See concept sheet on Site Selection.)

4. How large an area does the family feel comfortable with trying out (especially for beginners)?

5. How large an area does the family think it can prepare and manage? (What does "manage" mean?) See concept sheet on Feeding and Maintenance.

Some people say that a square field of 0.5 - 1 ha is the best size for rice-fish culture. However, operations larger or smaller than this "ideal" size can also be very successful. Good preparation and good management are the keys to success, whatever the size.

DIKES

All dikes must be built safely higher than maximum flood levels. During construction, the dike should be raised high enough to allow for compaction and erosion.

In raising the dikes, an excavation usually results. This may as well occur inside the field, all other factors being equal. This way, a small pond or trench is formed, which serves as a refuge for the fish.


Dikes

A - Existing ricefield

B - Small dike between field and pond/trench; optional but useful if fish are stocked in the pond/trench before rice is transplanted.

C - Side of pond/trench. Slope should depend on nature of soil: more gentle in sand, can be steeper in clay.

D - Level of water in pond/trench prior to transplanting.

E - "Lip" of existing field between pond/trench and dike, to prevent eroded material from filling the dike; usually 0.5-1 m wide.

F - Side of dike. Slope depends on nature of soil (gentle in sand). Top soil and grass planted on outside will reduce erosion.

G - Maximum flood level. Point G Is most Important. The dikes cannot be submerged by flood water.

H - Plants/trees grown on top of dike

I - Keep excavated topsoil and sods for the outside of the dike. Compact the soil during construction, as possible.

REFUGE

A refuge is a pond, trench or low point in the rice-fish field. When the rest of the field is dry, fish can be held here. Under some conditions (See Fry Nursing In Rice-Flsh Systems.), refuge may be stocked before rice is transplanted.

Having a refuge is usually advisable and may be necessary for success. Without it, fish have to be harvested before the field dries out or moved to a pond in a flooded area. A refuge of at least 50 cm depth is desirable. If the farmer wants to hold fish ail year around, it will probably have to be much deeper than this.

In some well-irrigated areas, a refuge may not be necessary. Some farmers find that digging a refuge increases water loss. This can happen in cases where poor soil (like sand) is covered by the top soil, which seals water in. Digging breaks this seal; it will re-form but this will take time. Manuring speeds up the process.


Refuge

A refuge, when dug, is usually made at the lowest part of the field so that water and fish can easily collect there.

Some other factors governing size and arrangement of refuges:

1. How much rice-growing area is the family willing to sacrifice for the refuge? This may depend on their total rice growing area or on the relative importance they give to rice and fish.

2. How much money or time and labor can the family invest? As with field size, this can be an important limit.

3. What kind of soil is involved? A narrow trench (say 1 m wide x 1 m deep) will fill in quickly in sandy soil, but may last well in clay. The refuge in sandy soil should be three or more times wider than its depth.

4. Topography will affect trench or pond configuration. Extensive peripheral trenches on sloping areas will occupy too much area since such a field will be narrow.

Consider these two fields, each of 16 sq m area:


Fields examples

The narrow field has the greater perimeter to area ratio.


Some Sample Refuge Layouts with Comments

Comments

Easy access for fish. Carrying excavated soil to dike can take time.

Easy access for fish. Best for large fields on very flat land. Can be expensive to build. Difficult entry for buffaloes.

Widely applicable on flat or sloping land, especially for plots of less than 0.5 ha (but can work for larger plots, too.)

When trench is on low side of field on sloping land with porous soil, seepage can be a serious problem. Digging trench below ground level (rather than merely damming at ground level) and manuring can help. So can excavating the trench on the uphill side of the plot and sloping the plot toward the trench. This, however, can take a lot of work


Sample refuge

A common set-up in rainfed Thai systems. Small pond for refuge, in a system consisting of many plots on gently sloping land. Pond is usually at or near lowest par! of field. Height of enclosing dike decreases as we go uphill. This can help water catchment. Accommodates small - scale environmental variation, with little work. Farmers should be careful fish have access to ponds when water is low

Narrow she low trenches connected! to refuges can be very helpful to fish trying to reach the refuges. One or two rows of rice may have to be scarified

DRAINS

Usually, the field will need a drain so that excess water can be removed rapidly without eroding the dike. Inflow and outflow drains are advisable, the latter particularly so. Drains should be screened to prevent fish escape.

What material?

A bamboo, hollow log or pipe can be used, depending on availability. A screen should be placed at the point where the water enters. The screen can be a piece of fine netting or a flat piece of metal full of nail holes. A little gravel scattered under the pipe will reduce dike erosion.


A bamboo

Such a drain is best for small fields (less than 1000 sq m) with limited flow (especially fields used to nurse hatchlings or small fry). Screens need to be checked every few hours for clogging any time water rises to pipe level and this can be a nuisance.


Such a drain

In most fields, the drain consists of a simple breach in the dike. This is screened by thin splints of bamboo or similar material, bound or nailed together.

Fammers in the rainier parts of Northeast Thailand often use a "li". This is usually a bamboo chute, set at a breach in the dike at the lowest part of the rice field.


Bamboo chute “li”

The li slopes up slightly and narrows. Below the narrow end, a jug-shaped basket or net bag is set. Hence, water nins out along the length at the li but ultimately fale into a bag or basket which holds any fish washed out of the field. These can be eater,, sold or returned to the field for further growth.


A bag or basket which holds any fish washed

Some farmers use a simpler version, by setting a net bag supported by sticks next to the outlet drain.

Outflow drain level

What depth of water is best for the rice in the field? What is the greatest depth it will tolerate? Set the drain in the dike somewhere between these two levels.

What drain capacity?

A small pipe does not drain a large field effectively. The farmer will have to make a guess as to how wide the drain should be, based on experience. It is better to have the drain a little too wide than too narrow.

Prepared by: JOHN SOLLOWS

FARMER-PROVEN INTEGRATED AGRICU LTURE-AQUACULTURE:
A TECHNOLOGY INFORMATION KIT (llRR-ICLARM)

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)

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)

Rice management in rice-fish culture

Rice-fish culture can be carried out under rainted or irrigated conditions, in either direct seeded or transplanted fields. Timing of seeding and transplanting activities are affected by many factors (water availability, rice variety, etc.) but is not usually affected by the fish culture component.

Seedlings are best transplanted 25-30 days after seeding although the best age for traditional varieties may fall outside this. In practice, they often remain in the seedbed longer than this. Sometimes, droughts occur so that the fields are too dry to be transplanted and the farmer must wait for rain. In other cases, the family labor force is limited and the rice in the seedbed must "wait" until the family gets to it.

Most farmers find no problem in applying chemical fertilizers to their rice-fish systems. In some cases where fish have died after exposure have been reported, fish had been fed with pellets and may have ingested fertilizer granules for this reason.

The wide scale of rice-fish is still constrained by continued application of pesticides in rice-based farming. The use of pesticide is not recommended in rice-fish farming. In rice-fish culture, there are ways of controlling rice pests that do not need pesticide, such as:

· Quick submergence (for three hours) of rice plants in water. This makes the insects vulnerable to fish predation. Limitation: suitable before plants are taller than the dikes.

· Two persons can drag a stretched rope (50-100 m) across the ricefields to knock off the insects into floodwater, after which they can be eaten by the fish. Limitation: suitable before riceplants reach booting stage.

However, should a farmer insist on using pesticides, here are ways on how to do it.

1. Considerations in applying pesticides:

· Choose and apply properly pesticides that have low toxicity to fish.
· Minimize the amount of pesticide getting mixed with water.
· Apply at suitable time.

2. Considerations in preventing fish poisoning:

· Drive the fish into the sump, draining the field slowly before spraying: keep the fish in the sump until the toxicity in the sprayed field is gone.

· Increase water depth (+ 10 cm 0) to dilute the concentration of pesticides in the water.

· Flush water through the ricefield. Open the inlet and outlet of the field and allow irrigation water to flow freely during spraying. Begin spraying from the outlet end of the field. When one-half of the field is already sprayed, stop for a while and allow the pesticides to flow out of the field. Then, continue spraying towards the inlet end of the field until it is finished.

To do items (2) and (3) above, examples are: to apply powder pesticides in the morning when dew drops are still on the leaves; and to apply liquid pesticides in the afternoon when leaves are dry.

There are a number of less toxic pesticides in the market. (Examples are Parapest, Sumithlon, Dlpterex.) Proper application of a toxic insecticide like Furadan or Curaterr 3G can be made safe to fish if applied through solid incorporation during the final harrowing. Furadan is a systemic insecticide, the efficiency of which in controlling insect pests lasts about 50-55 days. Incidence of pests at this period can be controlled by spraying liquid pesticides. At this time, the rice plants are already at their full vegetative stage and the thick leaves will intercept most of liquid sprays, thus drastically reducing the concentration of pesticides reaching the water.

In It is best to wait until the rice is well-established before releasing seed fish, particularly if the fish are large. Once two or three tillers have appeared, one to three weeks after transplanting is the usual waiting period, depending on the state of the rice and the size of the fish or one month to six weeks after direct seedling.

Small fry (of about one inch length) can be stocked immediately after transplanting, without harm to the rice.

Rice Varieties: We have never seen a variety that does not work with fish, but some are better than others:

Deep water-tolerant varieties are preferable to those which thrive in only very shallow water.

In some areas where rainfalls are highly unpredictable, farmers prefer to wait until very late in the rainy season to stock fish. At this time, surface water accumulation will be at its yearly peak and the chance of flooding from later rains is very slim. In such cases, long-lived, late-maturing rice varieties are best.

Rice varieties which tiller rapidly or under a wide range of water conditions will allow farmers to stock earlier in many cases.

Farmers have succeeded with early and late-maturing photoperiod-sensitive and non-sensitive, glutinous and non-glutinous varieties.

EFFECTS ON RICE YIELD

Our experience indicates that rice yields rise on the average, by about 10 percent, in rice-fish situations. However, there is great variation from farm to farm so guarantees cannot be made.

Yields seem the most enhanced on farms with poor soil where fish are fed intensively. Possible mechanisms include:

· helps in increasing availability of nutrients for increased floodwater productivity and uptake by rice.

· reduces loss of ammonia through volatization after fertilizer application by preventing floodwater pH rise over 8.5

The greatest danger to rice has already been indicated: big fish will damage very young rice; otherwise, some rice varieties do not tolerate deep water. By using very sensible precautions, farmers are not likely to harm their rice yields.

Prepared by: JOHN SOLLOWS & CATALINO DELA CRUZ

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

Rice-fish benefits and problems

In discussing a technology with potential new entrants, it is important to acquire them with potential benefits and risks so that they can make as balanced a decision as possible as to whether or not to try out the technology. If they are not aware of the potential benefits, they may miss a chance to improve their standard of living. Ignorance of the risks can also lead to serious problems and reduce their self-reliance.

PROBLEMS AND LIMITATIONS

1. Rice-fish culture requires land. Landless farmers will have difficulties here unless they can make arrangements with the owner and seed arrangements must be mutually beneficial. Acquainting the owner with the benefits and problems associated with the technology will be important. The agreement should spell what part of production goes to the farmer and what goes to the owner. Will rent be increased? Will it be rearranged? Will all additional benefits from fish catches go to the farmer?

Can rice-fish culture on communal land be arranged for landless farmers?

2. Production cannot be guaranteed, especially in rainfed situations. Details follows:

· Good water management is essential but not always possible. Rain is not predictable nor controllable. Too much h water can IA lead to controllable Too much water can lead to flooding and escapes. Too little water inhibits growth and, in extreme cases, can kill fish. Fish cannot be cultured without water. (See other sheets on preparation of Field/Feeding and Maintenance.)


Good water management is essential

· Poor water quality can impede growth and cause death. This is rarely a problem in rice fields, but can be an issue in nurseries. (See sheet on Fry Nursing In Rice-Fish Systems.)

3. Pesticides and other toxic chemicals can kill fish and should be kept away from them. (See other sheets: Site Selection/Rice In Rice Fish Culture.)


Poor water quality can impede growth and cause death

4. Transport of seed fish and stocking should be carried out correctly. Seed fish are very vulnerable at these stages; carelessness can kill. (See other sheet on Stocking for Rice-Fish Culture.)

5. Predators can seriously reduce fish stocks. Food nursing can solve this problem to a large extent. Submerged snake traps of wire mesh can be used to drown snakes. Snakes and frogs can also be caught manually. Frog eggs should be removed when discovered and dried. Birds can sometimes be scared away.

6. Thieves are perhaps the most difficult predator to deter. Living near the field helps sometimes. Partly filling the pond with bamboo or other branches makes netting the fish difficult and submerged barbed wire will probably ruin any net it snags. Obstacles (rock or logs) placed on the dikes leading to the field makes access difficult at night. Watchdogs can also help.

7. Field preparation will demand a large investment of time and labor or money from the family. For poor farmers, labor availability often affects their ability to carry out the practice, limits the area they can prepare and affects the Intensity with which the system can be managed. Old and young couples with small children will be particularly challenged here. As a rule of thumb, a 1000-square-meter field will merely take more than ten eight-hour days to construct, it one person is doing the digging. A family with no time to feed the fish should stock lightly.

8. The farmer's managerial skills will increase in time. Many farmers succeed their first year, but many fail, as well. Failure among experienced farmers, however, is few.

9. Rice yields are occasionally reduced by rice-fish culture. This occurs most often when large fingerlings are stocked before the rice is well-established. The water in some fields as well may be deeper than desirable for some rice varieties. Sometimes, rice will lodge and fish will graze on the rice seeds.

10. Some farmers complain that wild fish catches are reduced in fields with cultured fish. Tilapia is most often indicated as the suspect. These farmers feel that cultured fish in large numbers can scare away wild species

11. Marketing problems can occur. A farmer can plan to keep his fish to sell when prices are high, but water shortages can force him to sell before this. Transporting fish to the market can also take time, especially when transport arrangements cannot be made beforehand. If a family plans to sell an important proportion of their catch: where, when and how will they sell it? Will this be easy?

12. Seed fish supply is a very common problem. A family may not always be able to get what it wants. Seed fish purchase usually occurs during transplanting season when demands for fish are high and farmers have little time and money.


Seed fish supply

In village where fish culture becomes widespread, the establishment of small hatcheries and nurseries deserves serious consideration. It is often advisable to encourage two or more interested villagers' who feel that they are in a position to manage such operations, if the local market is sufficient. This will keep one producer from monopolizing the market.

BENEFITS AND POTENTIALS

1. Compared to many technologies, rice-fish culture is low risk. It demands little money, is not particularly "new" or revolutionary for most rice farmers and involves few-conflicts with other farm activities.

2. Fish cultured in rice fields provide farmer with a continuous, predictable, convenient supply of food. Farmers accustomed to depending on uncertain, declining stocks of wild fish appreciate this.

3. Rice-fish culture saves farmers time and conserves water. This allows many farmers to begin other Income-earning activities or to improve on existing ones.

4. The small amounts of money needed mean that farmers need not take out loans. They, therefore, have many options as to how to use their fish: They can eat them, sell them, keep them alive (nature permitting), preserve them or give them away. They do not have to make quick sales to reduce debts.

5. Income from sales can provide useful money at various times. Some farmers can sell brood fish or seed fish, as well as table fish.

Pest control mechanisms


Fish feeding on newly hatched snails.


Fish feeding on dispersing stemborer larvae.


Fish feeding on hoppers that fall on the water surface. Fish may actively shake rice hills when nibbling on the stems.


Fish feeding on case worm larvae while floating on the water.


Fish feeding on floating sclerotia.


Weeds are controlled by direct feeding. Increased water turbidity and constant flooding.


Disturbed moths fly up and are preyed upon by birds or other predators.

Prepared by: MATTHIAS HAIWART

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

The rice-fish ecosystem


Simplified nutrient flows

FERTILIZER - input of simple nutrients to the system

· Organic - available also to fish, plankton, algae, soil, fauna and bacteria
· Inorganic - available only to rice crops, macrophytes, algae, weeds, phytoplanktons and bacteria.

PHOTOSYNTHESIS - produces food from simple nutrients using sun's energy

- plants, algae and phytoplankton are food for fish, insects, zooplankton and soil fauna

DECOMPOSED MATERIALS - add to the detritus layer
BACTERIA - organisms which recycle materials back to simple nutrients
FISH - examples of various feeding groups


Ecosystem components


Ecosystem components A


Ecosystem components B


Ecosystem components C


Ecosystem components D


Ecosystem components E


Ecosystem components F

Prepared by: AHYAUDIN ALI

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

Fish as a component of integrated pest management (ipm) in rice production

INTEGRATED PEST MANAGEMENT (IPM)

IPM is a pest control concept that uses the best available mix of technologies for a particular pest problem. It promotes practices available to the farmer and permits pest control with the least use of chemicals to get high yields and maximum profits. Reducing pesticide application is an important factor because this control method is often uneconomical and unsafe to humans. Moreover, many pesticides kill both pests and their natural enemies at the same time, leaving the crop open to an uncontested invasion of pests.

IPM includes a variety of technologies such as choosing pest and disease-resistant varieties, using crop rotation, fallows and simultaneous planting over wide areas. It also encourages the establishment of natural enemies of rice pests.

Economic threshold levels are used to help farmers decide when the application of pesticides is economically justified. The presence of parasites and predators, including fish, minimizes the need for the farmer to take action.

FISH AS PREDATORS IN RICE FIELDS

The most widely spread fish species in paddies are common carp (Cyprlnus carplo), Nile tilapia (Oreochromis niloticus) and silver barb (Puntius gonlonotus). However, there is a large additional number of both stocked and wild fish species in ricefields.

Among those, there are larva-feeding and mollusc-feeding fish which are of considerable importance in the control of human vector-borne diseases, like malaria and schistosomiasis. Plant-eating fish species directly feed on weeds and are reported to be efficient in keeping irrigation canals free from vegetation. Turbidity and high water level add to the effects of fish-controlling weeds.

Different fish species will affect difenent pests in different ways. Common carp, for instance, appear very effective at controlling the golden apple snail. In Malaysia, tilapia was not able to control this pest but the giant walking catfish performed well.

The effectiveness of fish in fields where rice is broadcast is doubtful, since the rice will be too crowded to give fish good access to the field. There is no evidence for an optimal fish stocking density for pest control, but higher densities are presumed to be more effective. Fish eat older, outer rice leaves which are more likely to be infested with pathogens. This will make the rice plants healthier.

There are several reports documenting either reduced number of pests or less damage caused by pests and diseases with the presence of fish (Table 1). Most of this work has been done in concurrent rice-fish systems. In some cases, the underlying mechanisms have been described (Fig. 1-7). However, this list is far from complete. It is likely that more direct and indirect effects will be revealed with continuing research.

Problematic organisms in rice production, predation of fish and susceptible life stage of prey.

PROBLEMATIC ORGANISMS

PREDATION BY FISH

LIFE STAGE OF PREY

Insects



Whorl maggot

?

?

Gall midge

+


Caseworm



Leaffolder

?

?

Stemborer


Larvae

Black bug

?

?

Brown plant hopper


Nymphs/Adults

Whitebacked plant hopper


Nymphs/Adults

Green leafhopper

?

?

Diseases



Rice blast

?

?

Sheath blight

+

Sclerotia

Bakanae

?

?

Brown spot

+

?

Bacterial blight

+


Bacterial leaf streak

?

?

Weeds



Grasses

+

Seedlings

Sedges

+

Seedlings

Broadleaved weeds

+

Seedlings

Others



Golden apple snail


Hatchlings

? - no information available
+- based on documented observation

OUTLOOK

To date feeding habits of fish in the ricefield habitat are not well-established.

· Feeds can be given daily at 5% of the shrimps' body weight (If no manure loading) or 2-3% (with manure loading). Mix ingredients thoroughly, form them into balls and put them in feeding trays. The use of feeding trays controls consumption of feeds and prevents wastage.


Feeds can be given daily

· Feed twice a day: one third of the quantity in the morning and the rest in the aftermoon.

· Check feed consumption daily to adjust the feeding regime as necessary. Below is a recommended formula for shrimps in rice paddies.

50% - rice bran, broken rice or rice grain
20-30% - cassava root or broken maize
20-30% - trash fish, shrimp head wastes or oil cake

PREDATOR PREVENTION

Predators include sea bass, tilapia, snake head and other wild fish that compete with the shrimps for feeds. Predation can result in very low shrimp yields.

Before stocking shrimp, use any of the following measures:

· Drain rice fields and apply lime at the rate of 10 kg/100 sq m (15-20 kgs for sulphate acid soils)
· Apply Derris root (Derrls elilptica), 1-1.5 kg soaked in 10l water/1000 sq.m
· Release ducks into the rice fields for several days.

Within the culture time: Put gill nets in the trenches to catch the predators going to the rice fields.

CARE AND MAINTENANCE

· Water exchange is essential to supply oxygen to the shrimps and to remove detrimental substances in the water. This should be done at least twice a month. The more frequent the water is changed, the more suitable it is for the shrimps' growth and development.

· Water exchange also improves the pH value in the fields especially in sulphate acid soils.
· Dikes should be repaired yearly.
· Cover crab holes along the dikes to prevent leakage.
· Daily-check the screen mesh on the outlet and inlet pipes.

HARVESTING

· Harvest shrimps 5-6 months after rice harvest.
· Open the outlet pipe at low tide and drain the field and trench.
· Hand-collect shrimps in the rice field and use a net to harvest in the trench.


Harvesting

· Harvest only the trig shrimps (bigger than 15 9). The small ones are reserved for the next culture.

Note: Transfer small shrimps immediately to a hapa (cage net) to keep them alive for the next culture.

Bring harvested shrimps as soon as possible to the dealer or keep them in ice so that they stay fresh.

LAND PREPARATION AND TRANSPLANTING FOR RICE

· Local varieties are recommended. Transplanting should be done when the salinity is lower than 5 ppt.

· Plough and harrow thoroughly before transplanting.

· Transplant 30-40 days after seeding.

FERTILIZING

· Apply 50 kg diammonium phosphate and 5 t manure/ha before ploughing.
· Use 50 kg urea/ha for top-dressing

PEST CONTROL

· No pesticide or herbicide is applied in integrated shrimp-rice culture.
· Use brown planthoppe -resistant varieties of rice.
· Release one-month old ducks into ricefield to feed on insects, especially hoppers.

Note: In case the above measures cannot control pests, pesticide application can be an alternative. Before applying the pesticide, drain water in the field to let shrimps take refuge in the trench for 35 days.

MONOCULTURE OF SHRIMP IN THE FIELDS IN DRY SEASON

· Nipa and coconut trees are indicators of salinity lower than 10 ppt. Rhizophora is an indicator of salinity higher than 10 ppt.

· During the dry season when salinity level is not suitable for rice growing, the fields can be used for shrimp monoculture.

· Freshwater prawn (M Rosenbergll) can be grown if the salinity is not higher than 10 opt. The procedure is similar to those applied in the rainy season. When the salinity is higher than 10 ppt, freshwater prawns become stunted.


Monoculture of shrimp

· Tiger prawn (Penaeus monoden) and banana shrimp (Penaeus mergulensis) can be cultured in rice fields when the salinity is higher than 10 ppt in the dry season.

Stocking density

1/sq m

Stocked juveniles

2 g/head

Feeding rate

2-3% of body weight

Feed formulae

50 % rice bran (broken rice), 50% trash fish (tidder crab, oil cake)

Culturetime

5-6 months

Other procedures are similar to freshwater prawn culture.

Estimated cost and return of rice-shrimp culture In coastal areas in south vietnam (for one hectare).


VND

Costs


Rice seed (24 kg x 2,500)

60,000

Prawn seed (4,000 seeds x 60)

240,0Q0

Fertilizer (20 kg urea x 2,500)

50,000

Feed (100 kg x 1,000)

100,000

Manure (1 tm x 20,000)

20,000

Miscellaneous

20,000

Labor (20 man/day x 7,000)

140,000

Total Cost

950,000

Income


Rice (0.5 tm x 1,200,000)

600,000

Prawn (30 kg x 35,000)

1,050,000

Wild fish (4 kg 5,000)

20,000

Total income

1,670,000

Balance

720,000

1 US $ = 7000 VND

Prepared by: LE THANH HUNG

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