3 Planning: Selection of Fish

The farmer now has a firm idea of his site and the types of ponds it is possible for him to build. He also should know what he wants to do with his ponds -- raise fish for food or run a fish-marketing business. Now he must consider very carefully what type or types of fish he is going to raise in his ponds. The success of the pond depends upon choosing the fish that will grow best in the type of ponds and conditions that a farmer is planning.

The following pages give some: 1) general information on characteristics of fish, and 2) detail about certain fish which have proved to be good pond fish and why. This information should serve as a guide to a farmer trying to decide which fish will do best in his ponds.

Characteristics of Fish

The major body parts of all fish perform the same functions, and they are located in about the same places on any different fish's body. But the size, shape, and colour are often different, and these differences help tell the fish apart. Knowing how a healthy fish looks is important.

All fish have a tail consisting of the caudal peduncle and the caudal fin. The fish's fins help it steer through the water and hold it upright in the water. Often a sick fish cannot steer or flops over on its side. Other fins on the body include:

* Pectoral -- usually located on the sides of the fish behind the head.

* Pelvic -- usually located towards the rear of the body where the hips would be if the fish were a four-legged animal.

* Dorsal -- runs along the top of the fish. May be single or double. The second dorsal fin is sometimes called the soft dorsal fin.

* Anal -- usually located right behind the aral vent (anus) on the rear bottom end of the fish.

Most fish have eyes, but even with eyes fish cannot see very well. All fish have gills. The gills are covered by a flap called the Operculum. The gills are extremely important. Fish take in water through their mouths. The water is then passed through the gills which remove the oxygen and nutrients from the water. The water is then passed outside of the body of the fish through the gill slits.

It is possible to tell a lot about a fish's health and eating habits by looking at its gills. Fish with many, many feathery gill rakers and few if any teeth eat the smaller foods in the pond. Fish with few and larger gill filaments eat the larger particles from the pond. Healthy gills are a bright red colour. If the farmer sees fish with gills that do not have this healthy red colour, or have white spots all over, for example, he will know that fish is not healthy and should not be bought or placed in his pond. Or if the fish is already in his pond, he knows he must take steps to get rid of the disease before it troubles more fish.

Other identifying parts that all fish have are the mouth, the genital openings (to reproductive organs), and the lateral line. The lateral line is a small line of nerve cells which runs along the length of the body about midway on the side of the body. Sometimes the lateral line is covered by a layer of scales; sometimes it is a different colour than the rest of the body. In any case, the lateral line is an area of sensitivity that helps the fish feel pressure and temperature changes in the water around it.

Some fish, like catfish, also have barbels, small projections that hang down from the sides of the mouth. Barbels help the catfish sense its surroundings, find food, and attract small fish to the catfish so that it can eat them.

When a farmer breeds fish he will want to be able to tell the difference between male and female fish. This can be difficult with some fish. However, some fish change colour in the breeding season (tilapia, for example), so they are easy to identify by sex. Some fish can be classified according to the colour and size of their genitals. The separation of fish by sex is best learned by actual experience in the pond.

When the farmer goes to buy fish, he must already know what healthy fish look like. It is very important that he be as familiar as possible with each of the fish he decides to raise. He must know the characteristics of that fish and its life cycle, its eating and breeding habits, etc. The farmer who begins any fish pond enterprise without having this kind of information is inviting failure. And if it is a new venture, it is particularly important that the farmer's first effort be as successful as possible.

The Life Cycle of Fish

Fish start life as fertilized eggs. The eggs grow and then hatch into small fish, called fry. The fry are attached to the yolk sac which is the leftover part of the egg they hatched from. The yolk sac provides food for the fry during the first few days after hatching.

After the yolk sac is gone, the fry searches for food in the water. All fry eat the tiny suspended and swimming plants and animals called plankton in the water. Plankton are hard to see, but if a farmer puts some of his pond water into a glass container and holds it up to the light so that the light shines through the water, he can see the tiny plankton floating in the water. The length of the fry stage depends upon the species of fish. Usually a fish is a fry at least until the yolk sac is absorbed. Fry range from 2mm to 30mm in length. This growth process can take 2 to 6 or 8 days depending upon the type of fish.

As the fry grow bigger, they are called fingerlings. They are called fingerlings because at this stage of the growth cycle, they are about the size of a person's finger. Fingerlings vary in size -- from 4-1Ocm. Above 10cm, the fish is better called a post-fingerling. The adult fish ranges in size; some can be as large as 2m long and weigh 22kg. An adult fish is a fish which is sexually mature.

Fingerlings have different eating habits from fry; they are now much bigger and can eat larger pieces of food. As fingerlings, the fish begin to show that they like certain foods better than other foods. Each kind of fish chooses its own kind of food, depending upon his needs and what is available. For example, a carp fry will eat plankton; as a fingerling, the carp eats pieces of decayed matter and insect larvae; as an adult the carp will eat plankton, decayed matter, insect larvae, worms, snails, and almost anything that is on the bottom of the pond. Common carp, for example, are called "bottom feeders," because they eat food from the bottom of the pond.

The food preference does not always change as the fish grows. Some fish, like the silver carp, eat plankton their whole lives. When the fish reach adult size, they will sexually mature in the right conditions. Brood fish are sexually mature fish which are chosen as good fish to breed (spawn), produce eggs and begin the whole cycle again. This is called the life cycle of a fish.

Knowing how the fish in the pond grow, and the foods they require at each stage in the life cycle, is very important for good pond management.

Choosing Pond Fish

Choosing fish to grow in ponds can be difficult. A good pond fish has certain characteristics which help it grow successfully in ponds. There are some fish which will not adapt to pond conditions and cannot be used in pond culture. A pond is very different from a natural waterway:

* There is usually no water flowing through a pond. Some fish need to live where there is quite a bit of current in the water, rather than in a quiet pool of water.

* The food that is already in the pond is all that is available to the fish, unless extra food is put in by the farmer.

* There is only a certain amount of water and pond area in which to move about.

There are many fish that do grow well in ponds. Some of these are fish grown locally; some are fish grown in other parts of the world.

Many governments today are introducing exotic fish species (these are kinds of fish not native to that country) into fish pond programs. They do this for three reasons:

* Some Introduced fish grow better and faster than native fish.

* Some introduced fish are preferred by people for eating (over local fish).

* The offspring of a cross between a local fish and an introduced fish sometimes grow faster and taste better than either of the parent fish (this is called hybrid vigor).

But exotic fish must be watched and used very carefully. They must not escape into local waters. Some exotic fish which escape create problems in natural waters when they begin to compete with local fishes for food. Also, introduced fish can carry diseases or parasites that are fatal to native fishes.

There are certainly a number of fish in the natural waterways of your area which will grow well in ponds. Native (local) fish are usually easier to use because they are adjusted to local water and climate conditions.

If at all possible, farmers should be encouraged to start their ponds using a tested pond fish which is locally available and is well-liked by people in the area. It can be a fish from the list given here or one chosen from a list prepared in your area. The important points are that the farmer be able to sell any fish he wishes to sell, that the fish can grow in ponds, and that there is brood stock available locally.

Fish Used in Pond Culture

Here are some characteristics that good fish for pond culture will have. Certainly it may not be possible for a farmer to determine whether a certain fish has all these characteristics right away, particularly for those local fish not discussed in detail here or those newly introduced to pond culture. But good pond fish all have certain characteristics: the more certain a farmer can be that the fish he chooses to raise fit these descriptions, the more sure he can be of his success. Good pond fish are:

* available locally

* able to reproduce (breed) naturally in your area.

* able to live in a confined space (the pond).

* able to find the right foods in ponds.

* fast-growing.

* relatively free of parasites and diseases.

* known and liked as a food fish in the area.

Some fish that fit these criteria for good pond fish and are now grown in ponds all over the world are named here. Though they all are grown in ponds, each has certain characteristics which mean that it will grow better in some kinds of ponds better than other ponds. Of course, these fish are not the only fish that can be used in ponds. But they are named here because they have been tested in ponds, and they can grow well under pond conditions. All of these fish are warm water fish.

SCIENTIFIC AND COMMON NAMES OF FISH USED IN POND CULTURE

Please note: Each fish has a scientific name which is always the same. The common name, however, can be different from one country to the next. It is a good idea for anyone who works with fish to know the scientific name.

Genus - species Common name

1. Anguilla japonica eel

2. Aristichthys nobilis bighead carp

3. Barbus gonionotus tawes

4. Carassius auratus goldfish

5. Carassius carassius crucian carp

6. Catla catla catla

7. Chanos chanos milkfish

8. Cirrhina molitorella mud carp

9. Cirrhina mrigala mrigal

10. Clarias batrachus catfish

11. Clarias macrocephalus catfish

12. Ctenopharyngodon idellus grass carp

13. Cyprinus carpio common carp

14. Helostoma temmincki kissing gourami

15. Heterotis niloticus -

16. Hypophthalmichthys molitrix silver carp

17. Labeo rohita rohu

18. Mugil cephalus mullet

19. Mylopharyngodon piceus black carp

20. Osphronemus goramy gourami

21. Serranochromis robustus -

22. Tilapia macrochir tilapia

23. Tilapia melanopleura tilapia

24. Tilapia mossambica tilapia

25. Tilapia nilotica tilapia

26. Trichogaster pectoralis snakeskin gourami

27. Trichogaster trichopterus three-spot gourami

Following is specific information on some of the more popular pond fish.

COMMON CARP

The common carp, Cyprinus carpio, is a favourite warm water pond fish. Common carp are used as a pond fish because they:

* spawn easily in ponds.

* do not get sick easily.

* tolerate wide ranges of temperature and pH (factors of water quality discussed in detail later).

* eat all kinds of food, from zooplankton to decaying plants.

* have a very good growth rate.

* accept supplementary foods.

Common carp generally are a grey-green colour. However, they also can be gold, yellow, orange, pink, blue, green, or grey. They spawn all year round in warm waters, and they can be made to spawn by the pond owner if they do not spawn naturally. Common carp are good to eat when they are cooked properly. They can be grown in ponds by themselves (monoculture) or in ponds with Chinese or Indian carp (polyculture).

Some of the yields gotten in various countries by stocking common carp in monocultures are shown in the following table.

Yields,

Country Culture methods kg/hectare

Czechoslovakia Growth in ponds with ducks 500

Guatemala Intensive culture in ponds 4,000 India Natural growth in ponds 400 Growth in ponds with management 1,500  

Indonesia Intensive culture in ponds 1,500

Japan Intensive culture in ponds 5,000

Nigeria Commercial culture with fertilization and feeding 371-1,834

Philippines Intensive culture in stagnant water 5,500

United States Intensive pond culture with inorganic fertilization 314

Source: Bardach, et al (1972)

Conclusion: Common carp are a very easy fish to breed, keep, and harvest, so a fish pond that relies on common carp will probably do well. Common carp are a good fish for a farmer to use for his first effort. With good management, common carp will continue to produce healthy eggs and fry until they are too old (above 5 years of age).

TILAPIA

The Tilapia genus (family Cichlidae) contains at least 14 species, which are all good pond fish. The colour of the fish differs only slightly depending upon species; tilapia are generally dark brown to black in colour. The most common species grown in ponds is the Tilapia mossambica, also called the Java tilapia. It has been introduced throughout the world and is easy to find in most places. Tilapia:

* are hardy fish, resistant to disease.

* breed easily in ponds.

* grow rapidly.

* taste good.

* can withstand wide temperature ranges.

Tilapia are herbivorous: some species eat higher plants; some eat phytoplankton. Both the Java tilapia and the Nile tilapia (Tilapia nilotica) do well in very enriched waters (waters polluted by sewage). All tilapia have slightly different eating habits, depending on the species.

Tilapia reproduce every month or so, once they become sexually mature. They then take very good care of their own eggs and fry in ponds. If the farmer plans to breed and raise fry, this fish is a good choice because the fish themselves take care of the fry at a stage where many fish of other species die easily. The major problem with raising tilapia in fish ponds is that they become sexually mature at a small size, and begin to reproduce instead of to grow further. It may be necessary to separate the tilapia by sex before they are old enough to reproduce. Or it may be necessary to introduce catfish into the pond to control the population of small fish.

Conclusion: Tilapia species have many possibilities for pond culture. Their fast growth rate, ease of breeding, good taste and hardy bodies make them a good choice, particularly for the first-time fish farmer.

CHINESE CARPS

Other kinds of carp, besides the common carp, often are grown in ponds. Most commonly used are the Chinese carps. Some of these are:

* Silver carp (Hypophthalmichthys molitrix). This fish eats phytoplankton, but will accept rice bran and bread crumbs. The silver carp gets its name from its silver colour. It has very small scales.

* Bighead carp (Aristichthys nobilis). This fish feeds mainly on zooplankton. It is a dusky green colour on top which fades to a pale green colour on the abdomen. It also has small scales.

* Grass carp (Ctenopharyngodon idellus). This fish is an herbivore and eats water vegetation (but also will eat almost anything). The grass carp is also silver-coloured, but has a darker grey area running along the top of the body. It grows larger in size and has larger scales than a silver carp.

Other chinese carps like the black carp (Mylopharyngodon piceus) and the mud carp (Cirrhina molitorella) are bottom feeders. This difference in eating habits is very important in fish pond culture. It is the reason why polyculture, or growing a number of fish species in one pond can be successful. When one kind of fish is stocked alone in a monoculture, the foods in the water not eaten by that type of fish are wasted. In a polyculture of the above three species of Chinese carp, for example, three kinds of food are being eaten.

The following table gives some examples of polyculture mixes and of how many fish of each kind can be stocked in a pond. For example, Pond I is stocked with silver, bighead, grass and common carp.

STOCKING RATES OF CHINESE CARPS IN PONDS 3 TO 7 METERS DEEP IN KIANGSU PROVINCE, CHINA

Weight of Number of Yearlings per hectare

Species Yearlings, grams

I II III IV

Silver and bighead carp 500 4,500 4,500 9,000 9,000

Grass carp 500 600 - 3,000

Black carp 500 - 450 3,000

Common carp 200 200 200 200 200

TOTAL: 5,300 5,150 12,200 12,200

Source: Bardach, et al (1972)

The preceding table shows polyculture mixes: as you can see, common carp can also he used in polyculture with Chinese carp. Chinese carp are grown in ponds because they grow well in polycultures, and they are very good to eat. The silver carp grows faster and is tastier (according to some farmers) than common carp. The grass carp is most often used to control weeds in the pond. In fact the grass carp does a better job of weed control than do chemicals. The grass carp is perhaps the most interesting of the Chinese carp and is now being studied by scientists in many countries to find better ways of breeding it in ponds.

A farmer might run into problems raising Chinese carp -- if he does not look into his local situation very well. Farmers will have to have a source of Chinese carp fry from a government hatchery or a local breeder before trying to raise Chinese carp. The carp only breed once a year, and then, in most cases, only with help from man. Also, Chinese carp are very susceptible to diseases. Then, because they are delicate fish, they must be handled very carefully, or they will be injured.

Conclusion: A farmer just beginning a fish pond probably would not want to breed Chinese carp, but he certainly should be familiar with these fish and how they might help his ponds. For example, even two or three large grass carps placed in a pond with many fish of one other species, could be valuable for keeping a pond balanced.

INDIAN CARP

There is one last group of carp often cultured in ponds. These are the Indian carp. Indian carp are further divided into minor and major carp. The major carp of India are the catla (Catla catla), the rohu (Labeo rohita), and the mrigal (Cirrhina mrigala). The minor carp are the reba, the bata, the sandkohl, and the nagendram fish. The Indian major carp will not spawn in standing water, so special ponds are built in India to provide a flow of water for these fish, who must have running water in which to spawn. The Indian carp can be made to spawn by man, but this is a difficult process (see "Managing Brood Stock"). However, there seems to be no reason why the Indian carp cannot be spawned in ponds in places where ponds can be constructed to provide constantly running water.

Conclusion: A farmer who has only a small pond should not try to breed Indian carp. Indian carp can be grown in polycultures with common carp, but are not as good or fast growing in ponds as the Chinese carp. Indian carp are also susceptible to many diseases. This is a fish for an experienced fish farmer who is interested in, and able to, experiment.

GOURAMI

The gourami (Osphronemus goramy) is a very good pond fish. It is originally from Indonesia, but now is grown all over Southeast Asia. Gourami possess an accessory air-breathing organ, which means that they can survive in waters that are low in dissolved oxygen. This makes it' an important fish in areas where the temperature remains high and there is little water for certain periods of the year. Gourami spawn all year round in warm water conditions. Gourami:

* spawn easily all year round in warm waters.

* taste good.

* are easy to breed.

* accept a variety of foods.

* are hardy.

Conclusion: Gourami are good fish for a first-time fish farmer. And they are certainly a fish to be considered very thoughtfully by farmers who live in areas that remain very hot and dry for periods of the year. The gourami is used to these conditions, and there are other pond fish which would not do well at all under these conditions.

CLARIAS CATFISH

Clarias catfish are found throughout Asia, India, and Africa, as well as the Middle East. The species most often used as pond fish are Clarias macrocephalus and Clarias batrachus. Clarias macrocephalus is preferred for its good taste; Clarias batrachus grows faster.

These catfish have accessory air-breathing organs; they can even crawl out of ponds to look for food. Because they can live in shallow ponds, these catfish are sometimes used in culture with rice (see paddy culture). They are scavengers, which means they will eat just about anything. However, they prefer to eat worms, snails, and other fish. They are often used in polycultures with tilapia where they serve as predators on the very small tilapia. They will eat supplementary foods, and give very high production in ponds. In Thailand, Clarias catfish yield about 97,000kg/ha when they are fed supplementary foods. These catfish are hardy: they sometimes get external parasites, but these do not kill the fish.

Conclusion: The catfish are another good fish to be raised in areas where high heat and long dry spells are found. They are good to eat, easy to keep, and can be used in ponds in a number of ways. Certainly a farmer who already cultures paddy rice might be interested in considering adapting his paddy to catfish culture.

TAWES

The common name tawes is applied to three species of fish -- Barbus gonionotus, Puntius javanicus, and Puntuis gonionotus. These fish usually are used in fish ponds for vegetation control, in polycultures with Chinese carp. Tawes are able to spawn all year round, but they most often spawn in the rainy season. Tawes need well-oxygenated water with a strong current to spawn. Tawes feed on soft water plants, but will also take rice bran. There is not a great deal known about the tawes at present, but it can be used in polycultures when the grass carp is not available.

Conclusion: A farmer starting a polyculture certainly might be interested, in using this fish. However, first-time fish farmers with limited space would not want to try breeding this fish.

HETEROTIS NILOTICUS

The Heterotis niloticus spawn easily in ponds. The mature fish will build a grass-walled nest in the weeds at a pond's edge and spawn inside this nest. They spawn when water is low and very warm, at the end of the dry season. The mature fish feed only on plankton, but in a pond they will accept supplementary food. This fish has a swim bladder which can serve as an accessory air breathing organ.

Conclusion: There is not yet a great deal known about the Heterotis niloticus as a pond fish. But it seems that it is a good choice of fish for warm climates and warm waters. A farmer who lives in such a climate might find raising, and even breeding, this fish quite easy -- particularly in a very well-fertilized pond.

OTHER GOURAMIS

These are the snakeskin gourami (or Sepat Siam -- Trichogaster pectoralis), the three-spot gourami (Trichogaster trichopterus), and the kissing gourami (Helostoma temmincki). All of these fish taste good. And they breed easily in well-oxygenated, warm water. They do require a pond which has a good growth of vegetation (particularly Hydrilla verticillata).

Conclusion: In a pond situation such as that outlined above, these gouramis are easy to breed and raise. They are a good fish to use in polycultures with other gouramis, tilapia, and common carp.

MILKFISH CULTURE

The milkfish (Chanos chanos) can be raised in freshwater even though it is primarily a brackishwater fish, and will not breed in ponds. The fry are caught along the shoreline at breeding season (the rainy season) and transferred to freshwater ponds. Milkfish culture is done for the most part in the Philippines and in some other Southeast Asian countries, like Indonesia and Taiwan.

Adjusting (acclimatizing) the fry from the saltwater to the freshwater pond is hard to do; many fish die if the adjusting process is not done well. Therefore, milkfish usually are cultured in brackishwater ponds only; the use of milkfish in freshwater ponds is not widespread. Milkfish feed on a complex of bottom algae, and, recently, it is reported they also feed on phytoplankton. Milkfish are prized for their beauty and their good taste, though they have many, many small bones.

Conclusion: This is not a fish for the first-time fish farmer. In fact, it is not a good choice for any farmer unless he has a saltwater pond; is interested in trying to acclimatize the fish to a freshwater pond; or can buy milkfish from a source that has them already in a freshwater pond.

EEL CULTURE

Eels (Anguilla sp.) have been cultured in Japan and Taiwan for years. Eels are very much a luxury food and are not normally grown alone in ponds outside of these two countries. The eels are grown in ponds in polyculture with other fishes and are particularly useful in polyculture with species of tilapia because they eat the smaller tilapias. The eels used in Taiwan (Anguilla japonica) spawn in the sea and the fry (called elvers) swim upstream and are collected by dealers. Eels must be fed supplementary feeds like pellets made of trash fish.

Conclusion: It is not recommended that farmers work with eels because they must be fed protein and are not very efficient converters of food. Also, eels cannot be bred in fish ponds.

OTHER POND FISH

Some other fish grown in ponds are the goldfish (Carassius auratus), the crucian carp (Carassius carassius), and Serranochromis robustus. Any of these fish can be grown in polycultures with Chinese, common carp, and tilapia.

Conclusion: The use of one of these fish in a pond stocked with other, more important fishes, results in an increase in yields of both species. In polycultures these species can utilize other food sources and also act as predators and weed controllers.

One other fish species used in freshwater ponds is the striped mullet (Mugil cephalus). Like the milkfish, the mullet is primarily a saltwater fish, and its fry are collected as they swim upstream. Recently the mullet has been made to spawn by man, but this is difficult to do because mullet are very sensitive to handling. However, mullet can survive in wide temperature ranges and are herbivores, so some farmers may want to try mullet.

A CLOSING NOTE ON FISH

All these fish have been and are now being cultured in fish ponds around the world. However, as stated before, they are not the only fish which can be grown in ponds. In every area there are a number of fish in natural waters that could be grown in fish ponds. So you might find it a good idea to experiment with local fish in your ponds, to find those fishes that might be available to farmers in your area for use in their ponds. It is better for an extension worker to do the experimenting than it is to have a farmer risk wasting his time or money, or even more importantly, risk failure. If a farmer fails, he may not want to try again.