2 Planning: The Site and the Type of Fish Farm

Before construction can begin, the farmer must look over his land to choose the place or places where ponds can be built, and decide what kind and how many to build. He must also decide on the kind of fish culture he wants to do, and on the type of fish that he wants to raise. He must look at his resources and his needs very carefully before he actually begins building and operating a fish pond. This section will give information to guide the farmer in the planning of ponds and kind of fish culture.

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The Site

One of the most important parts of planning is finding the right place (selecting the site) for the pond. Fish ponds use the land in a different way from agricultural crops such as rice or wheat, but fish also are a crop. And when a farmer builds a fish pond, he is choosing one use of his land instead of some other use. If the site for the pond is well-chosen, the pond can be more productive than the land by itself. But if it is not chosen well, the farmer may lose, or, at best, gain nothing from his fish pond. When considering a site for the fish pond, the farmer should remember and consider several points that were made in the introduction:

* Often poor agricultural land can be turned into very good fish ponds. In general, the better the soil of an area, the better the fish pond. But this does not mean that a pond cannot be built on poor land. It does mean that the farmer will have to work harder to maintain the pond and the fish.

* If the pond is built on agricultural land which is not producing good crops, but the pond is cared for well, eventually the pond bottom soil will become more fertile than it was before. If this pond is a large one, after harvesting the fish, the pond can be planted again with a land crop, like corn, and allowed to grow. Then when the corn is harvested, the land can be turned back into a fish pond. This means that a farmer can get two good uses out of his land instead of one poor crop.

* Other farmers may want to grow fish in rice paddies by digging trenches around the edges of the paddy for fish to swim in. This is another way of culturing fish which will be discussed in somewhat more detail later in the manual.

The point of the discussion above, is that a fish pond is just one use that a farmer's fields can have, and the choice of how the land can be used is important.

There are three factors that work together to make a good site for a fish pond:

* Water supply

* Soil

* Topography

WATER SUPPLY

Water supply, soil, and topography all are important, but water supply is the most important factor in selecting a site. Fish depend upon water for all their needs: fish need water in which to breathe, to eat, and to grow and reproduce. If a site has water available year-round, that site meets its first test easily. If water is not available all the time but there is some way to store water -- in large tanks, barrels or drums, in depressions, ponds, or wells -- for use when the natural water supply is low, then that site may still be all right. The key, of course, is that water must be available at all times and in good supply.

Where Can Water for Fish Ponds Come From? Water used in ponds comes from many sources:

* Rainfall. Some ponds, called "sky" ponds, rely only on rainfall to fill their need for water.

* Run-off. Some ponds are gravel and sand pits which fill when water from the surrounding land area runs into them.

* Natural waters. Most ponds are filled with water that comes from natural springs or wells, or with water that has been channelled (diverted) and brought in from streams, rivers, or lakes.

* Springs. Some ponds are built where there is a spring to supply water. Spring water is water under the ground that has found a way to get out. It leaves the ground and becomes a stream as it flows away. Spring water is good for fish ponds because it is usually clean (uncontaminated) and has no unwanted fish or fish eggs in it. If the water from a spring has travelled very far, it may need to be filtered before it is used for a fish pond. But filtering is easy to do (see the "Construction" section) and the important fact is that the water supply is available.

* Wells. The best source of water for a fish pond is well water. Well water has few contaminants and, if the well is a good one, the water is continuously available. Well water and spring water, however, are both often low in oxygen content. Fish need to have oxygen in their water to live. Since this problem is overcome easily (see water quality information in the section on "Preparing the Pond") the major factor to be considered here is an adequate water supply.

Most fish ponds use water that comes from a stream, river, or lake. A diversion ditch or channel is dug between the water source and the pond to take water from source to pond. This is a good way to fill a pond because the water can be controlled easily. When the pond is full, the channel can be blocked with a gate or a plug (see "Construction" section), and the water will stop moving into the pond.

There can be problems with this kind of water supply; for example, often in tropical areas streams flood in the rainy season. This extra water can be dangerous to the pond and must be diverted away from the pond by a channel built for that purpose.

IT IS BEST NOT TO CHOOSE A PLACE THAT IS KNOWN TO FLOOD WHEN CHOOSING A WATER SUPPLY AND SITE FOR A POND.

When a pond floods, all the fish escape, and the pond is empty at harvest time.

If the water for the pond is being taken from a stream, lake, or river, then the farmer should plan to filter the water carefully when filling the pond. Water from these sources sometimes contains unwanted fish or fish eggs. Filtering prevents these fish or eggs, and other harmful animals, from entering the pond.

Quality of the Water Supply. Finding an adequate water supply is the first step. Then the farmer has to check that supply to make sure it can be used for a pond. This check of the water should include:

* looking at the water, smelling it and tasting it.

* looking to see if there is a family upstream who take baths in the water before it gets to the pond.

* making sure that there is no family or village downstream that depends upon the source for their drinking water.

If the water supply seems all right, the farmer must also find the answers to some other questions. Where the water comes from, how far it travels to get to the site for the pond, and what kind of soil it travels over will all affect the quality of the water. These questions and their answers tell what must be done to make the water right for a pond:

* Is the water very clear? Then the farmer may have to fertilize the pond because there are not enough nutrients in the water.

* Is the water very muddy? Then it will have to settle before it is used in the pond: a special place will have to be made where the mud can settle out of the water before the water goes into the pond.

* Is the water a bright green? It probably has a lot of fish food in it.

* Is the water a dark, smelly brown? It may have acid in it, and the farmer will have to add lime to the water.

There are many things which can be done to make water good for a pond. If the farmer knows his supply and the kind of water he has, he can take the steps necessary to use his supply well.

SOIL

The second important part of site selection is the soil of the area. The soil of the pond must be able to hold water. It also contributes to the fertility of the water because of the nutrients it contains.

Ability of Soil to Hold Water. The best soil for a pond contains a lot of clay. Clay soil holds water well. When a place with a good water supply is found, the farmer must test the soil. He can tell a lot about the soil simply by feeling it. If the soil feels gritty or rough to the touch, it probably contains a lot of sand. If it feels smooth and slippery, it probably means there is a lot of clay in it. This smooth soil is good for a fish pond.

A very good way to tell if the soil is right for a fish pond is to wet a handful of soil with just enough water to make it damp.

Then squeeze the soil.

If it holds its shape when the farmer opens his hand, it will be good for a pond. Remember, the more clay in the soil, the better it is for building a pond.

If the soil is sandy, or does not contain much clay, the farmer can still build a pond. There are ways of building ponds in these soils. But he should be aware that building a fish pond in such soils requires more effort and may not be as successful. Digging test holes will tell the farmer what his soil is.

Larger ponds can be built in soils with clay. If the soil is rocky or has shifting sand, etc., only small ponds are possible. If there are other locations available, the farmer would be wise to see if there is another place with soil better suited to the fish pond. More information on soil is included in the "Construction" section.

Ability of Soil to Provide Nutrients. Soil also contributes to the pond's fertility. Fertility is a measure of the nutrients in the pond, and it simply refers to how much food there is available in the pond for the fish to eat. A very fertile pond is one which contains a lot of fish food. The soil of the pond contains some of these necessary nutrients -- like iron, calcium, and magnesium. In addition, however, soil also can contain acids; these substances often are harmful to fish. Whatever a soil has in it is drawn into the pond by the water and thus comes in contact with the fish. Sometimes after a heavy rainstorm, there are big fish kills in new ponds. This happens because the heavy rain carries larger amounts of acids from the soil into the pond. So the farmer who is aware of the kind of soil he has for his fish pond can prevent this problem before it happens.

REMEMBER:

One good indicator of the quality of soil is whether it has been used for growing crops. If crops grow well in that location, the soil will probably be good for the fish pond. If crops did grow well there before the nutrients were used up, then it will probably still be free of harmful substances.

TOPOGRAPHY

The third factor in site selection is topography. Topography is a word used to describe the shape of the land -- whether it is flat or hilly, upland or lowland, etc. The topography of the land determines the kinds of ponds which can be built. Ponds can be built in valleys or on flat ground. They can be square or rectangular, or uneven in shape. They can be large or small. All of this is determined by topography of the land, as well as by the farmer's requirements.

The most useful topography for fish ponds is that which allows the farmer to fill and drain ponds using gravity. Ponds built on a slope, for example, can be drained easily. If ponds are located on flat land, the pond must be built with a slope inside it so it can be drained by gravity, or it will have to be drained using a pump.

Slope. If the farmer looks at a hillside, he can see that it rises. It is higher at one point than at another. This difference in height, from high to low point, is the slope of the land. In more scientific terms, slope is the relationship between the horizontal distance (length) and the vertical distance (elevation) over a piece of land.

Slope is usually written as a ratio (1:2) or as a percentage (5%). A slope of 1:2 means that for every change in length of 2 meters, there is a change of 1 meter in height. A slope of 5% means that for every change in length of, say, 100cm, there is a change in height of 5cm. Pond bottoms usually have a slope of 2-5%, whether they are on level ground or in a hilly area. As long as the pond bottom has a slope, it can be drained completely.

A farmer does not require a scientific understanding of slope to build a pond. He does need to know how the shape of his land determines the best place for building ponds. Ponds built in hilly places often are made part of the hill. The picture on top of the next page, of a pond with a spring as a water source, shows how the slope of the land has been used to set up the pond's drainage system.

In flatter areas, ponds are usually square or rectangular because it is easier to use a harvesting net in ponds of these shapes.

The farmer will learn quickly to recognize by sight the slope that is best for a pond. Because a slope is so important, the first thing a farmer should look for is a site with a slope and a water supply. If he can use a natural slope for his pond, the pond will be cheaper and easier to construct.

The best places to look for such combinations of slope and water supply are where water collects from streams and flows through the valley at the bottom of a slope. If the pond is built on the slope above the water flow, water drained from the pond can flow directly into the stream. Water might be brought to the pond in a number of ways depending upon the situation -- by streams running down the slope upon which the pond is situated, for example. Another good place to look for a good combination of slope and water supply is on plains or flattish ground between hills. These plains often receive water from brooks or streams.

There are many possibilities. The important thing is that the farmer look for a topography that makes fish farming as easy and as successful as possible.

The Type of Fish Farm

After the farmer has found a site or sites for his fish pond, he must consider what kinds of fish culture are possible in the space he has available. He also must decide what his resources will allow him to get started. This planning is necessary because the answers will determine the number of fish ponds the farmer builds and the kind of fish he will want to culture. The following pages present a range of ideas concerning the kinds of fish farm operations (raising fish or breeding fish); the types of pond used in fish culture; fish culture in one or several ponds; advantages of small and large ponds; and mixing or separating fish types and sexes. A discussion of these subjects will provide the farmer with the background he needs to decide what kind of fish farm is possible for him, given his resources and the kind of fish he wants to raise.

A NOTE OF CAUTION

Before a farmer even begins, however, it is important for him to include in his planning the fact that some fish will die. This is an extremely important fact for the first-time fish grower to understand. It is very natural for some fish, the weaker fish, to die in ponds. As long as fish are protected in ponds and are well taken care of, fewer fish will die in ponds than would die in natural waters. But a farmer who does not expect some death may get discouraged and give up before he has given his pond a chance to work. It is never too early to introduce this idea.

KINDS OF FISH FARM OPERATION

In nature, many fish never reach adult size because they are eaten by other animals (predators), or they die from disease or lack of oxygen. In fish culture, the farmer tries to control the pond situation in order to produce more fish. In ponds, predators and so on can be controlled so that the pond yields more fish per hectare than do natural waters.

There are two major kinds of fish farms -- those which breed fish and raise the fry, and those which rear fry and fingerlings (the young fish) to market size. So the farmer, after finding possible sites, etc., must decide if he is going to breed his fish and raise the fry. Or if he is going to buy fry and fingerlings and rear them to market size, not getting involved in breeding.

Breeding fish requires more time and more ponds than simply rearing fingerlings. And building more ponds can be more expensive and require more ongoing management. So the farmer must finally determine his reason for raising fish: to eat; to sell; to use his land better; or all of these. He will have to have all these things firmly in mind so that he can:

* build the right kinds of pond.

* build the right number of ponds.

* stock the right kinds of fish.

TYPES OF PONDS

The types of pond a farmer can build depend on water supply, soil, and topography, the factors which were just discussed. The two types of pond most often built are barrage ponds and diversion ponds. Many aspects of the construction of these ponds are the same. The main difference between these two types of pond is the water source.

Barrage Ponds. These ponds are usually filled by rainfall or by spring water. A spring, for example, sends water flowing through a small valley or down a slope into a low place. Or a spring bubbles from the ground into a natural depression. The pond is formed by collecting water at the base of the valley and in the low places. The farmer does this by building a wall (dam) which holds the water inside what now is the pond area. The wall keeps the water from entering and leaving except as needed.

The number of pond walls the farmer must construct depends upon the land and on how he fixes his drainage system. A barrage pond usually needs only one wall -- the main wall between the water source and the pond area. One kind of drainage system called a sluice (see "Construction" section) can be used to let water both in and out of the pond. There are also a number of simple drainage systems which can be used that do not require any complicated construction.

Barrage ponds should not be built where the flow of water is too great: it is difficult to keep the water from breaking down the wall if the pressure of the water is too great. Brooks and streams which flow well, but not too strongly, make good sources for barrage ponds.

Even when the flow of water is not great, however, barrage ponds require overflow channels. Because, barrage ponds are usually built in low areas, they are likely to fill up in heavy rains. Overflow channels are any kind of system which can be set up to stop the pond from collecting too much water. The overflow takes extra water away from the pond. If this extra water is not taken out, the pond wall may break. Therefore, the overflow system is needed to help the drainage system handle the flow of water when there is too much water in the pond.

The overflow system can be wide grooves cut into the top of the wall toward the ends away from the middle; it can be large hollow tree trunks which are set into the tops of the wall and work as pipes to drain the water into ditches, or even to carry the water into storage areas for use later when the water supply is low. Another kind of overflow can be ditches, dug into the ground above pond level, which take the extra water away when the water rises to that level.

An overflow often is not screened, because if something large catches on it, the pressure of the water behind it might cause the entire wall to break. This fact results in a loss of fish at time of flooding.

Diversion Ponds. These ponds are made by bringing (diverting) water from another source like a stream or river. Channels are dug to carry the water from the water source to the pond.

Diversion ponds can be made in a number of ways. Sometimes a pond is dug in flat ground or can be made by slightly enlarging a natural depression in the land.

These ponds, like the barrage ponds, require walls depending upon the topography of the land, the drainage system used, etc. A pond dug in flat ground often requires four walls; a pond built in a natural depression may not.

With a diversion pond, the water is always brought to the pond instead of running directly into the pond. Water can be diverted in a number of ways. For example, a small stream which gets its water from a larger stream nearby can be dammed and used as a diversion channel to feed a pond. Or water can be diverted to a pond from an irrigation ditch which carries water to agricultural crops from a nearby well or lake.

A farmer may have one diversion pond, or if his space allows and the water supply is sufficient, he may have several. When a series of diversion ponds is built, they are built in one of two ways:

* Rosary system. These ponds are built one after another in a string. In this system, all the ponds drain into each other and must be managed as if they were one pond. Therefore, if the first pond in the series (the pond with the water inlet) is full of predators which must be poisoned, all the other ponds in the system have to be harvested (have the fish taken out) and drained before the first pond can be poisoned and drained.

* Parallel system. In this series, each pond has its own inlet and outlet. Therefore, each pond can be managed as a separate pond.

Each kind of pond is going to have advantages or disadvantages depending upon the farmer's situation. A parallel system of diversion ponds, in most cases, is a better system. But rosary systems are cheaper and easier to build, and therefore, more possible for some farmers to undertake. Also, if the water source is good, and can be kept free of predators and unwanted fish, and if the management of the pond is done well, a rosary system can be very successful.

Diversion ponds are often better than barrage ponds because they are less likely to overflow, and the water source is often more dependable throughout the year. But barrage ponds require less construction and are likely to be cheaper. In addition, for some farmers, barrage ponds are the best, and perhaps the only, way for them to use their land for fish ponds.

The art of constructing and planning a fish pond or fish operation is very much an individual thing. There are basic ways of using resources, for example, land and water resources. But the exact shape and type of fish pond must be decided by the farmer for his situation. There are many ways of making fish ponds which will work, and the "right" way for any given farmer is the way which works best for him. Many aspects of fish farming are determined by experimenting with pond operation, but much can be done by good planning before fish pond construction.

Therefore, the farmer must look at his sites and consider the types of ponds he can build from the viewpoint of the number, size, and depth of the ponds he is going to need. If, for example, the farmer thinks he has a good area for a diversion pond, but hits solid rock at 1m and needs a pond 2m deep, he can find this out before he invests a great deal of time and money. If he has room for two small diversion ponds and a barrage pond, or for a large diversion pond and a barrage pond, he can base his decision on what kind of pond to build upon the number, size, and depth of pond he needs for what he will be doing.

The Number of Ponds. The number of ponds depends on the possible sites and on what the farmer plans to do with his fish ponds. If he is going to raise fingerlings to market size, he will need one or a few "rearing" ponds. If a farmer plans a larger operation in which he will breed fish for the eggs and fry, he will need space for nursery pond, rearing pond, and a pond for brood stock. Nursery ponds can hold eggs and fry until they are fingerling size; rearing ponds hold the fingerlings until they are market size; brood ponds hold the fish to be used for breeding.

It is possible to breed fish in a corner of a large, single pond, and a farmer interested in raising fish for his own use may want to do this. But a farmer interested in marketing fish probably will want at least two large ponds. If he has two medium-large ponds, he can use one for rearing fingerlings and one for broodstock. Eggs and fry can be taken care of in very small ponds or even containers.

The Size of Ponds. The size of ponds depends upon the same factors -- topography, water supply, and need. Nursery ponds usually are smaller than rearing ponds because the fry are very small. The size of nursery ponds depends on the fish species being cultured. In fact, eggs and fry can even be kept in washtubs, oil drums or any other such container which holds enough water for the number of fry and is supplied with enough oxygen.

As the fish grow, they need more space. So rearing ponds are usually bigger than nursery ponds, and brood ponds are bigger than rearing ponds.

Sometimes a farmer will have to choose between one large pond or several smaller ponds. His site would allow him to decide either way.

Here are some advantages of small and large ponds:

Small Ponds:

* harvest easily and quickly

* drain and refill quickly

* treat for disease easily

* are not eroded by wind easily

Large Ponds:

* cost less to build per hectare of water

* take up less space per hectare of water

* have more oxygen in the water

* can be rotated with rice or other crops

For most farmers, a few small ponds are better than one or two large ponds. Farmers must also manage their agricultural crops, and it is difficult for them to manage large ponds. Also, most farmers just do not have a lot of land. A good size for a single fish pond is probably between 1 and 5 ares (100 and [500m.sup.2]).

Farmers are going to be most interested in working the fish pond into an already going farm as simply and easily as possible. This is why culturing fish in rice paddies is popular in some areas. In fact, fish ponds can be set up in almost any area where a rice paddy can be located -- even on steep hillsides.

Small ponds are easier to care for and construct. As a farmer gains experience, he can go on and build larger ponds. Starting small is a good idea until the farmer feels he knows what he is doing and is successful.

Depth of Ponds.

The depth of ponds depends upon the fish being grown. Fish species like different kinds of food, and the depth of the ponds affects the kinds of food produced by the pond. A common carp, for instance, eats worms and other bottom organisms and must have a pond that is not deeper than 2m. But when the carp are fry, they eat only plankton, the tiny free-floating plants and animals suspended throughout the water. So nursery ponds for carp fry are often only 0.5m deep. (As mentioned before, eggs and fry can be taken care of in almost any container which holds enough water and has enough oxygen.)

Other fish feed at other levels in the ponds depending on their life stage and on their own food preferences. A very deep pond will not produce as much food because the sunlight cannot light the water below a certain depth, and the plankton will not be able to make oxygen for the fish (see water quality). On the other hand, a very shallow pond might be turbid, covered by water plants easily, and become very hot. Most pond owners make sure that the water depth at the edges of the pond is at least 75cm to discourage water plants. It is best if the pond is about 75cm deep at the shallow end and up to 2m deep at the deepest end. This will give the best results with most pond fish.

THE ONE-POND OPERATION

If the farmer's site can only have one pond, his decision is easy. It is hard to breed fish when only one pond is available. Usually a single pond is used only for rearing fish from fry or fingerlings to market size. This is the case in small, backyard fish ponds that are used to supply fish for only one family. A good minimum size for such a pond is [15m.sup.2] in area and 1m deep. A smaller pond would probably not be worth the effort to build and maintain.

A single pond is stocked with the fry or fingerlings. For example, a pond of the size mentioned above could be stocked with 60 fingerlings. These young fish are cared for until they reach adult size. Then the pond is harvested (the fish are taken out). The pond area can then be prepared for a new batch of fish and stocked again.

One pond can provide a good food source for the family. However, rearing fish means that somewhere there must be a source of fry or fingerlings for use in the pond. The farmer must check his area carefully, so that he is sure the young fish are available before he builds one pond.

The source can be a river where he collects the young fish, or a local fish farm which breeds fish to supply farmers who have small ponds, or a government hatchery where the farmer can buy the young fish. If the farmer decides that he wants to breed fish in his pond, it is possible to breed some fish inside small nets placed in the pond. A single pond, though, is usually used just for rearing fry or fingerlings to a good size for food and market.

While one pond usually means that the farmer is wise to concentrate on raising one batch of fish from fry or fingerlings to market size, he still must decide what kind or kinds of fish he will raise in his pond. He can raise one kind of fish alone (monoculture), or he can raise several kinds together (polyculture).

MONOCULTURE

Monoculture is the culture of only one species (kind) of fish in a pond. It can be tilapia of one species, common carp, or any other single fish species.

Monoculture has some advantages. One advantage is in intensive fish culture practices, where fish are fed a lot of supplementary foods for fast growth. It is easier to give there foods if there is only one type of fish in the pond. Another possible advantage is that monoculture gives greater control over the age and sex of the fish. In monocultures, fish can be of all different ages and life stages, or they can be separated into fry, fingerlings or brood stock.

A monoculture allows a farmer who is unfamiliar with fish farming to get to know his one type of fish very well. And there is some advantage to this.

One disadvantage of a monoculture pond is that it is more likely for a single disease or parasite to kill all fish in the pond. Different fish are susceptible to different diseases. If only one fish type is present in the pond, a bad fish disease could easily infect and kill all the fish if it were not stopped in time.

In monoculture ponds, fish are harvested selectively by using nets which have meshes of different sizes. For example, if the farmer wishes to harvest larger fish for market or breeding, the net will not catch or hurt the fry or fingerlings, because they are too small to be caught by a large-mesh gill net. This allows the farmer to keep his pond in operation and producing fish for food all year.

Monoculture is the most common kind of pond culture. For a small fish farmer who is most interested in having a nearby, year-round supply of protein (and who does not have a lot of time or interest to give to the pond), a monoculture may be a very good idea.

POLYCULTURE

Polyculture is the culture of two or more fish species together in a pond. A good polyculture uses the natural food sources in a pond better: if the polyculture is mixed correctly, each of the species eats a different food from the pond.

Polycultures are more resistant to disease. Disease, if present, usually attacks the smaller, weaker fish, and the healthier fish continue to live and grow.

Fish stocked in a polyculture must be able to live together. And living together successfully means that the fish put into the pond together do not all need to eat the same food. A polyculture can have fish of any size or age -- as long as a balanced relationship is maintained.

Some examples of polycultures are:

* fingerlings of two or more species stocked together in a fertilized pond and left to grow. A good mixture in this kind of polyculture is a mixture of Chinese carp -- silver, grass, and bighead carp stocked together. The silver carp eats phytoplankton; the grass carp eats pond vegetation; the bighead carp eats zooplankton.

* A few large fish (brood size) are stocked with fingerlings of another species in a pond and left alone. A good example of this is stocking tilapia fingerlings together with a few adult-sized Clarias catfish. The catfish feed on bottom organisms and serve as a population control on the fry that are produced in the tilapia ponds. Since one of the problems which can be associated with culturing tilapia is overpopulation, this is a very complementary relationship.

* Another example of this type of polyculture is a stocking of any kind of fingerlings mixed with a few large grass carp for weed control.

Polyculture is a good way to use a pond, especially if there is only one pond to use. A careful examination of local fish and their habits should tell a farmer what kinds of polycultures are possible in his pond. The important thing to remember is that the fish must not compete with each other. If stocked and managed correctly, polyculture ponds can give maximum production to a fish farmer. In very practical terms, the farmer could raise as much as three times more fish in a polyculture of three species than he can raise in a monoculture pond of the same size.

MONOSEX CULTURE

A word should be said about monosex culture, even though few farmers will choose or be able to choose this way of operation. Monosex culture means growing only one sex of one species of fish in a pond. When only males or only females are stocked in a pond, all the energy of a fish goes into growth and not into reproduction.

An all-male stocking has faster growth rates than a mixed stock of males and females. So some farmers try to stock only males or females in a pond. One fish species that often is used in monosex culture is tilapia. Tilapia reproduce at a very small size, but when separated by sex, they do not develop their reproductive organs, yet continue to grow.

One way to stock a monosex pond is to separate the fish one by one according to sex during the breeding season. Often, at this time, fish change colour, and it is easier to sort fish by sex. Then the fish can be grown to a larger size.

In another method, people have been trying to obtain fish of all one sex by putting two different species of tilapia into a pond. When these fish breed, they produce either a monosex culture or a sterile hybrid. Three crosses do now produce 100% male offspring.

Crosses of Tilapia which Produce 100% Male Offspring:

MALE CROSSED WITH FEMALE

Tilapia macrochir X Tilapia nilotica

Tilapia mossambica X Tilapia nilotica

Tilapia hororum X Tilapia mossambica

There are no crosses that produce 100% female offspring as yet. Males are preferred because they continue to grow during the breeding season, when there are no females present -- even though they (the males) continue to build their nests in preparation for mating.

Monosex culture is a valuable method of pond culture, but is usually difficult to do: the hybrid crosses are very new; hand-sorting fish by sex causes many of the fish to die from stress. Even if the fish are sorted without stressing them, one fish of the opposite sex that accidentally finds its way into the pond can ruin the whole monosex culture. So monosex culture is generally not practiced by small-scale fish farmers.

THE MORE-THAN-ONE-POND OPERATION

A farmer who has a larger area to work with might wish to consider having two or three small ponds. Perhaps two ponds would be diversion ponds, and the third a barrage pond fed by a spring. Perhaps the farmer has room for only two barrage ponds. He does not want to keep eggs and fry in the ponds because it is harder to protect eggs and fry in barrage ponds. This does not mean he cannot breed fish. He can keep eggs and fry in an oil drum, washtub, or anything else as long as the water is clean and contains plenty of oxygen.

With three ponds, one pond can be the rearing pond in which fingerlings are raised to market size; one can be used to keep brood stock; and the third, and perhaps the smallest, can be used as a nursery pond where the eggs hatch and the fry grow to fingerling size. If the farmer does not plan to breed fish, then he can use all three ponds as rearing ponds. He should not do this, however, without thinking ahead to the harvest and making plans for marketing the fish he will grow, or preserving the fish for sale or use later.

The major difference between a large farm operation and a small one may be only the number of ponds. Three ponds is enough to have a full-fledged operating fish farm which includes breeding, selling fry and fingerlings to other farmers, and raising fry and fingerlings to market and brood size. Once the farmer is a skilled pond manager, these ponds should do well and provide a good return on his investment.

Until the farmer is experienced, however, it is better for him to start with small efforts and a smaller operation. Small pond failure is not as severe. Once the ponds are working well, the farmer can expand and build more and/or larger ponds. But he should be encouraged to start small. There are a lot of factors in fish pond management that are learned best by experience. But a bad experience will discourage, rather than encourage, the pond owner.

A FINAL WORD ON PLANNING PONDS

Good planning is a must for a successful fish pond operation. It is during the planning process, before any money or a lot of time and energy is spent, that many problems can be solved.

The farmer should keep in mind while planning that ponds do not have to have expensive equipment in order to work well. Far more important than the equipment are 1) an understanding of the general principles involved, 2) the selection of a fish or fishes that will do well in his pond (see next section, "Selection of Fish"), and 3) good daily management of the pond (see section 6, "Managing the Pond").