Seed, feed and fertilizers are the three major inputs of undrainable pond culture systems. Paucity of quality fish seed is even now considered as one of the major constraints in the development of freshwater carp farming. This is mainly due to the large-scale development of this farming system creating ever-increasing pressure on carp seed industry. However, construction of large- and small-scale carp hatcheries has provided enough support to this industry during recent years. Ideally, a farm should be self-sufficient with nursery and rearing ponds so that after meeting their own demand the surplus seed can be sold for additional farm income. Small, seasonal, undrainable village ponds are most suitable for this purpose. Procurement of feed is not a problem as most of the feed materials are village-based agro-industrial products and by-products and are readily available in villages and local markets. Only some feed additives are needed to be procured from towns. Animal manures are incidental to village-based allied agricultural and animal husbandry activities while fertilizers are readily available in the local markets throughout the year.
Except common carp, all the other five Indian and Chinese major carps, viz. catla, rohu, mrigal, silver carp and grass carp, cultivated under composite fish culture do not breed in pond conditions although they attain full gonadal maturity. However, they breed in bundh type tanks. The successful development of the technique of induced breeding through hypophysation ensures breeding of both Indian and Chinese major carps in captivity. Therefore the stocking materials are procured from three different sources, viz. collection by traditional methods from rivers, by induced breeding of carps and by breeding in bundh-type tanks.
The technique of spawn collection from rivers essentially consists of operating fixed filtration nets in marginal areas of flooded rivers during monsoon months, when the Indian major carps normally breed. Success of operations mainly depends on proper sites, suitable nets, monsoon flooding patterns, availability of sufficient brood stock and the success of spawning.
8.1.1.1 Spawn net and its operations
These are funnel-shaped nets made of fine mesh (1.5 to 3.0 mm) handloom nettings (Figs. 25a and 25b). The posterior end has a small round opening fixed on a bamboo ring. A small trough-like receptacle (gamcha) is tied to the ring where live spawn is collected. The net is fixed in marginal waters where depth of water is negotiable without any aid. River margins with gradual slopes are the most suitable sites. Water flow in the range of 20 to 60 cm/sec is desirable.
Figure 25a. Collection of Riverine Spawn
Figure 25b. Riverine Spawn Collecting Net
8.1.1.2 Site selection
A premonsoon survey should be conducted to collect the following details, based upon which the suitable site is selected.
The topography and terrain and river bank features in the vicinity of a site to determine the extent of area available for operating nets at different flood levels.
Topography of dry beds and bank features to know the likely current pattern of the river at different levels of flooding.
The distribution and composition of the fish fauna in the selected stretch of the river for assessing the resident population of Indian major carps.
Location of tributaries, streams, etc., along with their confluence with the main river as these may be connected with the breeding grounds.
The accessibility of the site.
Spawn availability is mostly associated with receding phases of floods.
8.1.1.3 Collection operation
To assess the availability of spawn, initially 2–3 spawn nets should be operated constantly at suitable sites and the whole battery of nets should then be introduced as soon as the spawn become available. The nets should be fixed along the river margins with the help of bamboo poles and are adjusted according to changes in flood level. At every four hours, the nets should be removed, cleaned and refixed.
The flowing spawn are collected in the receptacle (gamcha) from where they are scooped every 15 to 30 minutes, depending on the amount of spawn being collected. The collected spawn along with the bigger fishes, debris, etc., should be scooped from the receptacle (gamcha) and transferred to aluminium containers (hundies) half filled with water. The collection should then be sieved through round meshed mosquito netting to segregate spawn from debris and larger fishes, and the spawn should be conditioned in hapas (cloth compartments fixed in water) before they are transported. Measurement of spawn should be done by special sieve cups (Fig.26). Usually early spawn measures about 500 individuals/ml. The seed collected from rivers are generally a mixture of seeds of major carps, minor carps, predatory fishes, etc.
Figure 26. Sieve Cup for Measurement of Spawn/Fry
Bundhs are special types of perennial and seasonal tanks or impoundments where riverine conditions are simulated during monsoon months. The bundhs are ordinarily of two categories, viz., a perennial bundh commonly known as “Wet bundh” and a seasonal one called “Dry bundh” (Mookherjee et al., 1944) (Figs. 27A and 27 A-1, 27B and 27 B-1).
8.1.2.1 Wet bundh
A typical “Midnapore type” of wet bundh is generally located in a gradual slope of a catchment area with an inlet towards the high land and an outlet at the opposite side towards the lower end to regulate the inflow and outflow of water respectively during heavy showers.
The wet bundh contains a deeper area which retains water throughout the year and where adequate stocks of brood fishes are maintained. During heavy rains, a major portion of the bundh is submerged and excess water, if any, is drained through the outlet which is guarded by bamboo fencing (locally termed as “Chhera”). The shallow areas of the bundh (moans) serve as breeding ground for fishes present in the bundh.
The wet bundh varies in shape and size from place to place. Generally, the ponds covering a water body of 1–2 ha with catchment area ranging from 20–100 times are considered as wet bundhs, but a bundh could be as large as 300 ha.
Figure 27A. Bundh for Breeding (Wet Type)
Figure 27A-1. Bundh for Breeding (Wet Type)
Figure 27B. Bundhs for Breeding (Dry Type)
Figure 27B-1. Bundhs for Breeding (Dry Type)
8.1.2.2 Dry bundhs
This type of dry bundh consists of only one shallow depression (or one shallow pond) and a catchment area located in a gradual slope. The upper high land area is considered as a catchment area. The shallow depression or pond is enclosed by embankments on three sides which impounds freshwater from the catchment area during the monsoon season. There should be provision for an outflow for drawing excess water from the pond during heavy rains. The outlet is guarded by fine bamboo fencing. Such bundhs remain more or less dry during the greater part of the year. In the West Bengal Province of India, a catchment area more than five times the size of the bundh is considered most suitable (Saha et al., 1957), whereas in Madhya Pradesh the recommended ratio is 1:25 (Dubay and Tuli, 1961). Dry bundhs of Madhya Pradesh are comparatively bigger in size (0.2 to 2.5 ha) than those of West Bengal (0.1 to 0.5 ha).
In a modified bundh, adjacent ponds are constructed along the gradient of the catchment area (Moitra and Sarkar, 1973, 1975). The upper one where the premonsoon rain water is collected from upland catchment area serves as a “reservoir” and the lower one is used for breeding purposes. A deeper tench is dug along the lower extremity of the breeding bundh so that the breeders can take shelter before and after spawning. The reservoir and breeding bundhs are arranged in a sequence along the gradient so as to facilitate the flow of water which is controlled through a system of sluice gates. Premonsoon rain water is collected from the catchment area to fill up the reservoir. The water-holding capacity of the reservoir is generally more than that of the breeding ground bundh.
8.1.2.3 Breeding operation
Wet bundh: With the onset of monsoon the fresh rain water from the catchment area enters into the bundh and the latter is inundated. The excess water flows out from the bundh creating a water current. The breeders present in the deeper area of the bundh migrate to shallow areas where they start breeding.
Dry bundh: Rain water which accumulates in the catchment area during premonsoon showers flows in to fill up the pond seasonally. Thereafter, the brood fishes from a perennial pond are introduced into the seasonal ponds to breed, preferably on cool rainy days. Spawning usually commence during and after heavy showers when the bundh as well as the catchment area are flooded with fresh rainwater.
In a modified method adopted in Bankura and Midnapore districts of West Bengal, some fresh water is released from the reservoir into the breeding bundh. Gravid carps from the perennial ponds are then transferred to the breeding bundh. Generally, the ratio of male and female spawners is maintained at 1:1, but sometimes this proportion is not strictly followed. The spawners are allowed to remain for 10–12 hours in order to get acclimatised to the environment. A few sets of males and females are then selected and taken out from the bundh and placed in separated mosquito net hapas, which are cloth compartments fixed in water with the help of poles at its four corners (Moitra and Sarkar, 1973, 1975). The selected female breeders are taken out of the hapas and injected intramuscularly with fresh pituitary extract. The females are administered an initial dose of the extract at the rate of 3 mg/kg body weight and thereafter kept again in mosquito net hapas. After 4–5 hours, the second dose (8 mg/kg) of extract is injected to the female. At the same time the males are given the initial dose of the extract at the rate of 3 mg/ kg of body weight. The injected spawners are then released into the breeding bundh. After administration of the second dose of extract to the females, the inlets and outlets of the bundh are lifted to allow the entry of a steady flow of water from the reservoir into the breeding bundh soon after breeding takes place. In one such bundh 5–6 breeding operations can be taken up in one season, subject to availability of spawners and fresh water. Before starting the next breeding operation in the same bundh, the water is completely drained out and it is allowed to dry.
Exotic carps such as grass carp and silver carp have also been induced to breed in the dry bundhs of West Bengal by applying pituitary extract and under regulated water flow (Sinha et al., 1975).
Collection of eggs: Egg collection is taken as soon as the embryo starts twitching movements. To collect eggs, the water level of the bundh should be lowered by opening the outlet. Eggs are generally netted by a piece of thin cotton cloth (gamcha) or a piece of mosquito netting cloth. In such areas a series of earthen pits are constructed with water flow facilities. Fertilized eggs are allowed to hatch in these pits and the spawn are collected after three days. Spawn are usually sold at the bundh site.
As an alternative method, use of hormones for inducing spawning in Indian major carps has been in practice for the last three decades. The gonadotropic hormones secreted by the pituitary gland of fish play an important role in the process of maturation and spawning. As discussed earlier, under pond culture conditions, the carps do not spawn, although they attain maturity. This is due to the fact that the pituitary gonadotropic hormones which induce spawning are not released in sufficient quantities from the pituitary gland (hypophysis) to the general blood circulation so as to trigger spawning. Therefore, for induced spawning, the hypophyseal hormones extracted from the pituitary of donor fish are injected into the sexually matured fish under favourable water and climatic conditions during the monsoon season.
In India, the first success of induced spawning by hypophysation of Indian major carps was achieved by Chaudhuri and Alikunhi (1957). Subsequently, silver carp and grass carp were also bred in 1962 (Alikunhi et al., 1963). This outstanding success in induced spawning of Asiatic major carps has revolutionized carp culture practice through commercialization of carp seed production.
Pituitary gland of major carps and its collection:
The pituitary gland or hypophysis of Asiatic major carps is a small, pear-shaped, whitish soft body, situated on the ventral side of the brain below hypothalamus, which is connected to the pituitary gland by a funnelshaped structure, the infundibulum. The quantum of gonadotrophic hormones in the pituitary vary with the season and maturation stages of the fish and hence the degree of success achieved in induced spawning depends very much upon the condition of the pituitary gland of donor fish. Based on a series of experimental trials it has been found that the maximum success in induced spawning is possible with extracts prepared from gland collected during May/June, i.e. the period just before spawning (Moitra and Sarkar, 1978). Thus the pituitary glands for the induced spawning programme should preferably be collected from the freshly killed fully matured specimen of both the sexes of the same (homoplastic) or allied species (heteroplastic) during May/June when the potency of the gland remains at its peak. Well preserved iced fish are also suitable for this purpose. Common carp, a perennial breeder, has been found to be an excellent donor fish as the potency of the gland remains more or less high throughout the year. Both male and female donor fish are suitable for gland collection.
8.1.3.1 Collection of gland
The commonly adopted method of gland removal is by chopping off the skull with a sharp butcher's knife or a hand saw. The brain thus exposed is lifted up by detaching the optic nerve. Excess of watery fluid and the blood is soaked by absorbant cotton and then the membrane covering the gland is cautiously removed by using a needle and a pair of forceps. The gland thus exposed is picked up very carefully avoiding any damage (Fig. 28). Broken or damaged glands lose their potency due to hormonal drainage. In India, in fish markets where a large number of fish heads are sold separately and the consumers strongly dislike dissected fish heads for consumption, the glands are taken out from behind the head through the foramen magnum. The technique of removing glands by this method is simple and quick. Behind the head there is a big hole in the brain case known as the foramen magnum. The brain tissues are removed through this foramen magnum and then by close examination the gland is located embedded in the floor from where it is scooped out carefully with the help of a small scooper.
Figure 28. Collection of Pituitary Gland
8.1.3.2 Preservation and storage of glands
Freshly collected glands have been found to be the best for the induced breeding purpose. But when we need a large number of glands to take up breeding on a commercial scale, it is not always possible to sacrifice so many matured fish for the required quantity of glands. Such limitations dictate large-scale collection and preservation of glands from fish markets. There are several methods under use for the preservation of pituitary glands, the most popular being the preservation in absolute alcohol and after an interval of 24 hours they are dried, weighed and transferred to dark coloured phials containing fresh absolute alcohol. Alcohol dehydrates and defattens the glands. Details about the place and date of collection, the age and weight of the donor fish, etc., should be labelled on the phials for ready reference. The phials are then kept at room temperature or in a refrigerator. When needed the stored glands are put on filter paper which allows the alcohol to evaporate, and are then weighed accurately. However, better results have been achieved from glands preserved in acetone. Immediately after collection the glands are kept in fresh acetone and placed in a refrigerator. After two days the glands are taken out, weighed and replaced in phials with fresh aceton. Such phials are labelled and placed in a refrigerator until use. The glands can also be kept frozen. Fresh glands are frozen immediately after collection and kept in a refrigerator, deep freezer or in insulated cans containing dry ice.
8.1.3.3 Preservation of pituitary extract
Pituitary extract is normally prepared just before administration as such extracts cannot be kept long. However, there are certain simple methods for the effective preservation of pituitary extracts. The advantage of extract preservation is that the preserved material remains in the ready-to-use form which is very convenient, especially in villages where most of the basic facilities like precision balance, tissue homogenizer, distilled water, centrifuge, etc., for extract preparation are not available. Besides, extraction from a large number of glands also ensures uniform hormone potency per unit volume of extract. In such cases it is always desirable to ascertain the potency of such extract through several breeding trials before initiating a large-scale breeding programme.
Fish pituitary extract is prepared in distilled water-glycerine media at a concentration of 40 mg of gland for every ml of media. A known quantity of glands is taken and macerated in a tissue homogenizer. Distilled water equal to one-third of the total volume of extract is added to the fully macerated glands and thoroughly mixed. Pure glycerine, twice the volume of the distilled water, is then added. Thus the ratio of distilled water to glycerine is maintained at 1:2. The entire suspension is again thoroughly mixed and filtered through filter paper to remove tissue fragments if any. Prepared extracts can either be ampouled in ampoules of various capacities or may be kept in small phials in a refrigerator. Such extracts should be consumed within one breeding season.
8.1.3.4 Brood stock maintenance and their selection for spawning
The two major inputs of induced breeding programmes through hypophysation are the pituitary glands and the properly matured spawners. Success of hypophysation also depends on the condition of the spawner and hence proper attention must be paid to raise quality brood stock in adequate numbers. Preferably 2–3 years old healthy male and female carps should be selected and reared in well prepared ponds of 0.2 to 0.5 ha with minimum water depth of about 1.5 m. The stocking density should be kept at a relatively lower level ranging between 1 500 – 2 000 kg/ha. Normal pond management schedules are to be followed strictly involving weed clearance, removal of predatory and weed fishes, pond fertilization and application of supplementary feed, fish health care and monitoring of pond environment. Details about pond management are given in subsequent sections of this manual. Supplementary feed consisting of 1:1 oil cake and bran mixture should be applied daily at the rate of 1–3% body weight on underwater feeding plates. The addition of 15–20% fish meal, vitamin and mineral mixture to the conventional feed gives better results. For grass carp, aquatic weeds such as Hydrilla, Najas, duck weeds, etc., or green animal fodder such as napier grass, hybrid napier, barseem, etc., are to be provided at the rate of 20–25% of their body weight on a daily basis. The fish should be periodically netted and examined carefully to find out the stage of maturity and state of health. This rearing period normally lasts for 4–5 months. Proper care during this period ensures availability of well matured quality spawners for induced breeding programmes. It is estimated that for a target production of about 10 million spawn (6 million of Indian major carps and 4 million of silver carp and grass carp) about 750 kg of brood stock (300 kg of Indian major carps and 450 kg of silver carp and grass carp) comprising both males and females in a ratio of 1:1 by weight and 2:1 by number are required.
Usually after the onset of the monsoon when there is an accumulation of fresh rain water in the pond and a fall in atmospheric temperature, the breeding programme is taken up. The southwest monsoon period is the normal breeding season for these Asiatic carps in south Asian countries and usually extends from April to September. In some places the monsoon is early and hence the breeding season starts from April onwards. By seining the pond, spawners are caught and carefully examined for selection. Matured males ooze a milky fluid (milt), if the abdomen is slightly pressed near the vent. They are also characterized by the roughness of their pectoral fins. Matured females have a soft bulging abdomen with slightly swollen and reddish vent. A catheter is found to be quite helpful especially in the case of silver carp and grass carp in selecting the matured female breeders by examining the condition of the eggs. By inserting the catheter in the genital opening of a female spawner, some eggs are taken out and examined at the pond site in a petridish. Uniform size eggs of pale blue colour in silver carp and brown or copper colour in grass carp indicate proper maturation stage. Cool rainy days when the water temperature ranges between 25°C to 30°C are considered to be ideal for induced breeding. Ripe and healthy males and females of desired species are selected from the brood stock ponds, their individual weights are recorded using hand nets and a spring balance and the females are kept ready for the first injection of the pituitary gland.
8.1.3.5 Induced breeding operation
After the selection of brood fish the injectable dosage of pituitary extract is calculated in terms of milligram of pituitary gland per kg body weight of the recipient fish. Females are given two injections at an interval of 4–6 hours while males are given only one injection at the time of the second injection to the females. Considerable variations are noticed in the effective dosage of pituitary extract which depends mostly on the potency of the pituitary gland, gonadal maturity of the recipients and the prevailing climatic conditions. It has been experienced that a lower dosage is effective when extract is prepared from fresh glands while a higher dosage is required when commercially supplied glands are used for the purpose. The first and second dose in the case of females of Indian major carps may be given at the rate of 2–4 mg/kg and 5–10 mg/kg body weight respectively. The males are given only one injection at the rate of 2–4 mg/kg body weight at the time of the second injection to the females. Silver carp and grass carp females should be given at the rate of 3–4 mg/kg body weight during the initial injection and 8–10 mg/kg body weight during the final injection. Males receive only one injection at the rate of 3–4 mg/kg body weight. However, as stated the dose of the pituitary may be slightly increased or decreased depending on the local climatic conditions, potency of the gland and the response of the spawners.
After deciding on the dosage, the quantity of glands required for injecting the selected brood fish is calculated. Both ready-to-use bottled or ampouled extract or freshly prepared extract can be used. For the preparation of fresh extract the required quantity of glands should be taken out, blotted, dried and weighed accurately. The glands are then macerated in a tissue homogenizer with a small quantity of distilled water and further diluted so that each ml of the extract should be eqivalent to 20–40 mg of pituitary gland. The extract is thereafter centrifuged to get rid of tissue fragments and only the supernatant solution is utilized for the injection.
The spawners should be grouped into several sets. Each set should consist of both female and male spawners in the ratio of 1:2 and approximately 1:1 in weight. The required number of breeding hapas at the rate of one hapa for each set should be fixed in the pond. A breeding hapa is a rectangular cloth container (2.5 x 1.5 x 1.0 m) closed from all sides except an opening on one side with tying arrangements, through which spawners are introduced and taken out (Fig.29). These hapas should be fixed in the shallow waters of ponds, canals, lakes, and reservoirs with the help of bamboo poles in such a way that two-thirds of it are submerged in the water. Modern facilities such as breeding tanks of metal, cement, fibre glass, etc., or plastic pools with continuous supply of water having controlled temperature ensure greater efficiency and operational ease.
Figure 29. Breeeding Hapas in a Pond
Intramuscular or intraperitoneal injections are administered. Intramuscular injections are commonly given in the caudal peduncle region avoiding the lateral line. In the case of intraperitoneal injection the needle is pushed with ease at the innerside base of the pectoral fins. For intramuscular injection, the needle is inserted under the scale initially parallel to the body of the fish and finally pierced into the muscle at an angle of 45° (Fig. 30). The most convenient hypodermic syringe used for the purpose is of 2 ml capacity having 20 divisions. The size of the needle for the purpose is also important which depends on the size of spawner to be injected. The BHD needle No.22 is conveniently used for 1–3 kg of carp breeders and No.19 for larger ones. Needle No.24 can be used for small size spawners.
Figure 30. Injecting a Dose of Breeding Hormone
The induced breeding work is generally taken up on cool and cloudy days when the water temperature is around 25–30°C. It is always convenient to apply the first injection between 16.00–17.00 hours and the second injection after 4–6 h of the first injection i.e. between 20–23 hours. In the case of mrigal it is desirable to keep this interval of only 4 h. After the first injection to the female spawners, both males and females of the set are released in the breeding hapa or the breeding enclosure. At the time of the second injection both males and females of the set are taken out, injected as per prescribed doses (Table 8), and released back in the breeding hapa.
| Injection | Time of injection (h) | Female IMC | spawners* GC/SC | Male IMC | spawners* GC/SC |
|---|---|---|---|---|---|
| 1st | 16.00–17.00 | 2–4 | 3–4 | - | - |
| 2nd | 20.00–23.00 | 5–10 | 8–10 | 2–4 | 3–4 |
* IMC - Indian major carp; GC - Grass carp; SC - Silver carp
Breeding normally takes place within 3–6 h after the second injection. Recent investigation of Sinha (1972), has indicated that gonadal hydration is a prerequisite for successful spawning of carps. Gonadotropins induce the hydration process thereby increasing the body weight of the spawners, and thus serving as an indicator for the success or failure of the breeding programme. A 3% increase in body weight of female spawners between the two subsequent injections indicates better breeding success. The eggs are released by the females in the early morning hours and are fertilized naturally inside the hapa by the milt released by males. The brood fishes are removed from the hapas and the eggs which are non-adhesive and semibuoyant swell like small pearls of 3.5 – 5.5 mm in diameter. The total quantity of good eggs laid is estimated from the total volume of eggs and percentage of fertilization. Fertilized and viable eggs are transparent in colour while dead ones appear opaque under naked eye. Percentage of fertilization is scored from several egg samples examined in a petridish or watch glass. Silver carp and grass carp normally do not release eggs inside a hapa or a breeding enclosure even after being injected with hormone and hence these fishes have to be stripped and fertilized artificially. The females are examined 3–4 h after the second injection to see their readiness for stripping. Keeping the ventral side up and by giving a slight pressure at the genital opening, if the eggs are seen oozing out, the fish is considered to be ready for stripping. Otherwise they are released back and examined again after an interval of 1/2 – 1 h. Usually, the dry method of stripping is adopted where the spawners are wiped with a towel and then the female spawners are stripped and the eggs are collected in dry enamel basins and immediately fertilized with stripped milt from the male spawners. At this stage the eggs and milt are mixed thoroughly for 1–2 minutes with the help of a clean feather and subsequently the eggs are washed 3–4 times with water. The fertilized eggs are then kept in breeding hapas for a few minutes for proper swelling and hardening. The usual quantity of eggs obtained from Indian and Chinese major carps under field conditions are presented in Table 9. It has been observed that in silver carp males the quantity of milt is insufficient and hence extra males should also be injected to ensure maximum fertilization of stripped eggs.
| Species of carp | Approximate number of eggs/kg body weight |
|---|---|
| Catla | 125 000 – 200 000 |
| Rohu | 250 000 – 300 000 |
| Mrigal | 150 000 – 200 000 |
| Silver carp | 100 000 – 150 000 |
| Grass carp | Around 100 000 |
| Common carp | 150 000 – 250 000 |
8.1.3.6 Incubation of eggs and hatching
The eggs are measured by a graduated enamel or plastic mug of 1–2 litre capacity and collected in plastic buckets. From the plastic buckets eggs are collected with the help of a 1 litre mug and spread uniformly at the rate of 3–4 litres of eggs in double-walled hatching hapas fixed in ponds free from algal bloom, and predatory fish species (Table 11). These double-walled hapas are open from the upper side. The outer hapa is made of thick cloth or very fine meshed nylon cloth while the inner one is made of round meshed mosquito netting cotton/nylon cloth. The dimension of various hapas are given in Table 10.
| Type of hapa | Dimension (m) | Specifications | |||
|---|---|---|---|---|---|
| Length | Width | Depth | |||
| Breeding hapa | 2.5 | 1.25 | 1.0 | closed from all sides except at the opening with tying arrangement. Thick cotton/nylon cloth. | |
| Hatching hapa | |||||
| Outer | 1.8 | 1.0 | 1.0 | Upper side completely open. Thick meshed nylon/cotton cloth. | |
| Inner | 1.5 | 0.8 | 0.5 | Upper side completely open. Round mosquito netting of cotton/nylon cloth. | |
The number of eggs to be spread in each hapa depends on the size of the eggs of the species concerned. The following table will be helpful in deciding the amount of eggs to be incubated in a hapa.
| Species | No. of eggs/1 (Approx.) | Amount of eggs in 1/hapa |
|---|---|---|
| Catla | 22 000 – 25 000 | 4.0 |
| Rohu | 28 000 – 30 000 | 3.0 |
| Mrigal | 26 000 – 30 000 | 3.0 |
| Silver carp | 22 000 – 25 000 | 4.0 |
| Grass carp | 22 000 – 25 000 | 4.0 |
Hatching time is temperature dependent. Usually hathing takes about 15–18 h at temperature range of 26–31°c. At lower temperature the hatching time is considerably larger. The hatchlings pass out through the mesh of the inner mosquito netting hapa to the outer hapa. When hatching is completed, the inner hapa with egg shells is removed and the hatchlings are left undisturbed in the outer hapa for three days till the yolk sac is completely absorbed and the spawn become ready for stocking in nursery ponds. Common carp and other unwanted fish when present in the pond have been reported to cause severe damage to carp eggs in breeding hapas (Tripathi, 1975). The use of 1/4 inch mesh size drag net as a barrier to prevent common carp from destroying fertilized eggs in breeding/hatching hapas may be a suitable way to solve the problem of those fish farmers who have only one pond and utilize it for composite fish culture (Radheyshyam, Sarkar and Singh, 1985).
The hatching technique described above has, however, several drawbacks and large-scale mortality and loss of developing eggs and hatchlings may occur due to natural hazards such as a sudden rise of water temperature, development of algal bloom, depletion of dissolved oxygen, presence of predatory crustaceans, etc. With a view to improving the hatching technique and reducing mortality of hatchlings, a glass jar hatchery has been designed by the Central Inland Fisheries Research Institute (CIFRI) and found to be very useful in terms of percentage survival of hatchlings. Water hardened eggs are incubated in vertical hatching jars where the flow of water is so regulated during the incubation that the eggs are gently stirred without being spilled over. In each jar of 6.35 1 capacity, 50 000 eggs can be kept for hatching. Normally the rate of flow of water is kept at 600–800 ml/min for Indian major carps and 800 – 1 000 ml/min for Chinese carps. It normally takes 12–15 h for the developing eggs to hatch out in Indian conditions. Various modifications of this hatchery system are now available and extensively used. Chinese hatchery system consisting of cisterns with diagonally pointed nozzles as water inlets and outlet with filtering screen and valve are also becoming popular. It requires a large volume of water with sufficient pressure to create a circular water current in the hatching cistern. 700 000 to 1 200 000 fertilized eggs can be used per cubic meter of water. Spawn are collected through drainage outlet.
8.1.3.7 Post-spawning care of brood fish
It should always be remembered that spent carps are potential breeders for the next breeding season and hence they should be saved and properly cared for. Before releasing them back in the pond they should be given prophylactic antibiotic treatment. Streptomycin sulphate and penicillin at the rate of 25 mg/kg fish and 20 000 I.U./kg fish respectively in the form of injection has been found to be very effective in preventing post spawning bacterial infections and subsequent mortality. Before releasing them back to ponds they should also be given a dip treatment in potassium permanganate solution to prevent any fungal attack. In the case of silver carp and grass carp females, where stripping is the normal practice, recovery from shock and severe stress is difficult under Indian condition and hence they should not be released back into the broodstock pond. However, if the stripping is easy and fast, both the males and females can be released after giving the similar prophylactic treatment. Use of anaesthetics during stripping minimises shock and stress and brings ease in stripping operation.
Multiple breeding: Under natural conditions, Asiatic major carps breed only once a year. However, in recent years it has been possible to breed them twice in a year. They are induced to breed in the early part of the season, well cared and well fed for the rest of the season and during the end of the breeding season they are again induced to breed by the same techniques. The interval between the two breeding operations may vary from 30 to 60 days.
Common carp is the only fish cultivated under composite fish culture which naturally breeds in ponds throughout the year in Indian conditions with two peaks of spawning, one during January to March and the other during July/ August. The females deposit sticky eggs on leafy vegetation in the pond which are immediately fertilized by the males. Although they breed naturally in the ponds, the survival of spawn is always poor and hence they should be induced to breed under controlled conditions as per the following successive steps.
8.1.4.1 Segregation and care of mature fish
Healthy and matured male and female brood fish should be segregated and kept in separate ponds usually by April and October. A mature male easily oozes milt when the abdomen is gently pressed. The female on the other hand has a bulging abdomen with a papilla-like outgrowth with a median slit in the vent region. Segregated brood fish should be fed daily at the rate of 3% of their body weight.
Although they breed several times during the year, breeding should be taken up during mid-January to March and again during July-August.
8.1.4.2 Breeding technique
Fully mature male and female brood fish are selected for breeding and kept either in breeding hapas or cement cisterns. Breeding hapas should be fixed in the shallower region of the pond with the support of bamboo poles. A set of spawners consisting of one female and two smaller males more or less equal to the weight of the female are released in each breeding hapa. Sufficient quantity (double the weight of the female fish) of fresh aquatic weeds such as Hydrilla, Najas, Eichhornia (water hyacinth), etc., are also introduced in the hapa and uniformly spread. Fish usually spawn within 10–12 hours. Spawned breeders are then taken out and given prophylactic antibiotic treatment and released back to the pond. The difference in weight of the female before and after spawning gives the estimate of eggs released. Each gram of ovary contains about 700 eggs (Alikunhi, 1966). An allowance of 12–15% should be given for faecal droppings. By examining several samples of eggs, the percentage of fertilization can also be estimated. Fertilized eggs are dirty pale in colour and more or less transparent, whereas unfertilized eggs are opaque and whitish in colour. The weeds with attached eggs should be transferred to the hatching hapas (Fig. 31) fixed in the pond. About 1 kg of weed with attached eggs should be kept in each hapa. The incubation period depends upon the water temperature and varies from 36–72 hours. At a temperature of about 28–31°C the hatching takes place in about 45–50 hours.
The newly hatched out larvae are 4–5.5 mm in length with a prominent yolk sac. The newly hatched out larvae adhere to the leaves of the weeds and remain in this condition for some time. The yolk is absorbed within 2–4 days after hatching depending on the water temperature. The weeds are removed very carefully from the hatching hapas and the spawn are removed during the early morning hours. Collected spawns are sieved through a coarse mosquito netting cloth to remove debris, measured with a seive cup and transferred to nursery ponds.
However, this early stage of fish seed is not suitable for stocking in all types of ponds. The spawn is nursed for 2 or 3 weeks up to fry stage in nursery ponds and then the fry (2–3 cm) are transferred to rearing ponds where they are reared for three more months up to fingerling (8–12 cm) stage. This is the fingerling stage of the fish seed which should be used for stocking the composite fish culture ponds.
Figure 31. Hatching Hapas in a Pond
Undrainable ponds have the ability to continuously supply natural fish food for the cultivated carp species. But the quantum of the natural food usually available in the pond is not sufficient to support the dense fish population cultivated under semi-intensive and/or intensive fish culture systems. As such, natural feed is always supplemented with some artificial feed to achieve optimum production. A brief account of the natural food available in undrainable ponds and the supplementary feed used in fish culture in undrainable ponds is presented below.
Some of the cultivable fish species such as trout, salmon, eel, etc., are exclusively fed on artificial food. On the other hand, carps require natural food and many feel that at least 50% of the food ingested by them should be the natural food items. Hence the availability of natural feed is one of the major factors contributing to fish production in undrainable ponds. Natural feed, being balanced, not only provides the essential nutrients such as proteins, carbohydrates and fats, but also takes care of the much needed vitamins and minerals to the cultured fish which may not be present at the desired levels in artificial feed unless otherwise fortified. Natural feed, in addition, possess some of the essential amino acids and fatty acids required for growth while most of the artificial feed may be deficient.
8.2.1.1 Principal natural fish food
An undrainable pond ecosystem provides a wide variety of natural food to the fish. The following groups of organisms are important (Figs. 32A and 32B).
| A. | Phytoplankton: | Chlorophyceae | - Green algae | ||
| Bacillariophyceae | - Diatoms | ||||
| Myxophyceae | - Blue-green algae | ||||
| B. | Zooplankton: | Protozoans | - Sarcodines, flagellates and Ciliates | ||
| Rotifers | - Branchionus sp. | ||||
| - Asplanchna sp. | |||||
| - Keratella sp. | |||||
| - Polyarthra sp. etc. | |||||
| Crustacea | - Cladocerans | ||||
| - Moina sp. | |||||
| Cida sp. | |||||
| Ceriodaphnia sp. | |||||
| - Copepods | |||||
| - Nauplii | |||||
| Diaptomus sp. | |||||
| Cyclops | |||||
| - Ostracods | |||||
| - Cypris sp. | |||||
| Stenocypris sp. | |||||
| C. | Zoobenthos: | In addition to some species of Cladocerans and Ostracods, the following groups are also represented. | |||
| Crustacea | - Macrobrachium sp. | ||||
| Water mites | |||||
| Aquatic insects | - Odonatans, Hemipterans, | ||||
| Trichopterans, | |||||
| Lepidopterans, | |||||
| Coleopterans and | |||||
| Dipterans. | |||||
| Molluscs | - Pila sp., | ||||
| Viviparus sp., | |||||
| Lymnaea sp. and | |||||
| Lamellidens sp. | |||||
In addition to these, bacterioplankton, detritus materials coated with bacteria and periphyton are also equally important as natural fish food.
The aquatic bacterial community while regulating a large number of important processes in the pond energy flow and mineral recycling, also serve as food for several carp species. The quantity of bacterioplankton depends on the primary production and the added organic matter. In newly constructed and desilted ponds, the bacterial numbers are much less, whereas in old ponds the bacterioplankton population is found to be the highest.
Planktonic detritus particles associated with bacteria are freely suspended in the water column and they serve as food for filter feeders.
The sediment detritus constitute the food of benthophagous fish species which utilize it directly. Most of these particles originate from the decomposing macrophyte remains.
The fauna associated with the sediment and the macrophytes have relatively longer generation time than the planktonic organisms; even then they occupy an important place in the natural food resources for the pond fish. The natural food produced in the pond are varied and are able to cover the entire choiced food spectrum of all the six species of carps cultured together. Carp species have their own preference for natural food which varies with the different stages of their life cycle (Table 12).
8.2.1.2 Availability of natural food for fish in ponds
The availability of natural food to fish in ponds depends on the quality and the quantity of the standing crop which in turn is determined by the extent of exposure of the pond to fish culture, stocking density, species stocked, the size of the fish reared and on fertilization programmes. The sources from which the nutritive fauna develops in the ponds are numerous, the main among them being the portion of the ponds that never dried, the water which has been used to refill the pond, the bottom soil with organisms in hibernation or their encysted stages, wind-borne encysted organisms (copepods, cladocera, rotifers, etc.), eggs laid by insects, etc. In the presence of sufficient food and favourable environmental conditions, these fish food organisms multiply at a faster rate. Pond fertilization helps in increasing the amount of natural food in the pond through the supply of the necessary nutrients which are either lacking or are insufficient in the pond ecosystem. This helps the growth of primary producers - the phytoplankton and macrophytes which form the food of fish and herbivorous zooplankters. Organic manure containing practically all necessary nutrients required for biological production, encourages bacterial growth which in turn favour better production of zooplankton and increases the effectiveness of many inorganic fertilizers by providing necessary organic matter base. Details about pond fertilization with organic manures and inorganic fertilizers are discussed in the next section of this manual.
| Species | Stages of life cycle | |||
|---|---|---|---|---|
| Larvae | Fry | Fingerlings | Adult | |
| Catla (Catla catla) | Protozoans, rotifers unicellular algae, etc. | Protozoans, rotifers and crustaceans. | Crustaceans, algae, rotifers and some vegetable debris | Crustaceans, algae, rotifers, plant matters, etc. |
| Rohu (Labeo rohita) | - do - | Protozoans, rotifers, crustaceans, unicellular algae. | Vegetable debris, phytoplankton crustaceans, detritus, etc. | Vegetable debris, microscopic plants, detritus and mud. |
| Mrigal (Cirrhinus mrigal) | - do - | Crustaceans, rotifers, planktonic algae. | Vegetable debris, unicellular algae detritus and mud. | Blue-green and filamentous algae, diatoms, pieces of macrophytes, decayed vegetable matters, mud & detritus. |
| Grass carp (Ctenopharyngodon idella) | Protozoans, rotifers, copepod nauplii. | Protozoans, rotifers, crustaceans, microzoobenthos, detritus, microalgae, plant fragments. | Detritus and aquatic plants. | Aquatic plants such as wolffia, lemna, spirodela, hydrilla, najas, ceratophyllum, chara, etc. |
| Silver carp (Hypophthalmichthys molitrix) | Unicellular planktonic organisms, nauplii and rotifers. | Copepods, cladocerans and phytoplankton. | Falagellata, dinoflagellata, myxophyceae, bacillariophycea, etc. | Mainly phytoplankton. |
| Common carp (Cyprinus carpio) Var. Communis | Protozoans, rotifers, cereodaphnia, moina, nauplii, etc. | Rotifers, cyclops, cereodaphnia, moina, nauplii, euglena, oscillatoria, etc. | Diaptomus, cyclops, moina, cereodaphnia, ostracods, insects including chironomid larvae. | Decayed vegetable matter, worms, molluscs, chironomids, ephemerids and trichopterans. |
Figure 32A. Natural Fish Food Organisms (Phytoplankton)
Figure 32B. Natural Fish Food Organisms (Zooplankton)
Some of the fish food organisms such as rotifers (Brachionus sp.) and cladocerans (Bosmina sp., Moina sp., Daphnia sp.) can be cultured on a mass scale in earthen enclosures, plastic pools, tanks, etc, and may be inoculated into the nursery ponds. Cow dung and oil cake are applied initially at the rate of 250–350 ppm and 50 ppm respectively, and subsequently after every four days at the rate of half the initial dose. After the treatment, seeding is done with 2–5 ml of Moina sp., collected from nearby ponds. Moina thus cultured may be used for seeding nursery ponds at the rate of 30–50 ml of Moina/ha (Jhingran and Pullin, 1985). Chemical analysis of plankton show that on an average, crude protein constitutes 44% to more than 57% of the dry organic matter. Plankton has relatively small amounts of fat averaging to about 5–7%.
The fish production rate may be increased significantly by merely supplementing the natural food with artificial feed which can support more fish with increased individual weights, resulting in a more profitable operation. All the carp species including the predominently plankton feeders like catla and silver carp and macrophyte feeder grass carp accept supplemental feed.
8.2.2.1 Conventional feeds
The conventional supplementary feed is usually a mixture of brans and oil cakes in 1:1 ratio by weight. In India, oil cakes such as mustard oil cake or groundnut oil cake and rice or wheat bran are widely applied depending on their local availability. In Bangladesh, the most common fish feed is the mixture of mustard oil cake and rice or wheat bran. In Nepal, farmers are advised to feed a mixture having maize, wheat or rice bran and mustard oil cake. In certain regions, finely chopped vegetable matter or grass are also mixed. The same feed is applied in nursery, rearing and stocking ponds. Aquatic weeds or sometimes green animal fodder are given to grass carp. Smaller aquatic weeds such as wolffia, lemna, spirodela, etc., are provided in the early stages while large macrophytes and green animal fodder to the bigger fish.
8.2.2.2 Balanced supplementary feed
Using locally available feed materials and mixing with vitamin premix, essential minerals and trace elements, a balanced supplementary feed can be compounded without any significant increase in its cost which will give better results than the conventional one. However, the background knowledge of the nutritional requirement of carps becomes essential for formulation of suitable balanced supplementary feed.
The quantity and quality of nutrients required by carps for attaining optimum growth vary with the species, size and stages of the life cycle. Essential nutrients such as protein, fat, carbohydrate, vitamins and minerals are required as raw materials for the formation of body tissues, production of energy and also to regulate the vital physiological processes.
Protein: Protein requirements may be looked at the gross protein and specific amino acid requirement levels. Protein requirement is influenced by several factors like water quality, natural food availability in ponds, dietary protein quality, the amount of non-protein energy in the diet, stocking density, etc. Protein requirement levels of some carp species are given in Table 13.
| Species | Crude protein level in diet for optimal growth (g/kg) | Reference |
|---|---|---|
| Common carp | 450 – 480 | Sen et al., (1978) Sin (1973) |
| Rohu | 450 | Sen et al., (1978) |
| Mrigal | 450 | Singh et al. (unpubl.) |
| Grass carp | 410 – 431 | Dabrowski (1977) |
Though dietary protein levels have been shown as optimal for fry and fingerlings of Indian major and common carps (Table 13), quality of the protein in terms of its amino acid composition is important or else growth would suffer even if the dietary protein level is high. Plant proteins are deficient in certain essential amino acids like methionine. Their quality can be improved by the addition of animal proteins such as fish meal, bone meal, blood meal, etc. (Table 14).
| Amino acid | % of protein | % of diet | Total protein in the diet (%) |
|---|---|---|---|
| Arginine | 4.2 | 1.6 | 38.5 |
| Histadine | 2.1 | 0.8 | 38.5 |
| Isoleucine | 2.3 | 0.9 | 38.5 |
| Leucine | 3.4 | 1.3 | 38.5 |
| Lysine | 5.7 | 2.2 | 38.5 |
| Methionine + | 3.1 | 1.2 | 38.5 |
| Phenylalanine ++ | 6.5 | 2.5 | 38.5 |
| Threonine | 3.9 | 1.5 | 38.5 |
| Tryptophan | 0.8 | 0.3 | 38.5 |
| Valine | 3.6 | 1.4 | 38.5 |
+ In the absence of cystine
++ In the absence of tyrosine
Carbohydrates: Carbohydrate requirement of carp species is highly variable ranging from 10–45%. Common carp utilizes 25% carbohydrates effectively as energy source (Takeuchi, Watanabe and Ogino, 1979; Sen et al., 1978), while for mrigal fingerlings it is 28% in synthetic diets (Singh, Sinha and Kumar, (unpubl.). Although higher levels of carbohydrate may be utilized by carps, diets containing over 40% dextrin results in retarded growth and lowered feed efficiency due to lower digestibility. The most likely symptom of over supply of carbohydrates in diet is excessive deposition of fat in the liver and carcass. However, the protein requirements of carps can be brought down to some extent by raising the level of dietary carbohydrates.
Lipids: The polyunsaturated fatty acids (PUFA) is considered to be the most important class of lipids as far as lipids are concerned. Carps can derive their lipid requirement from natural feed available in the pond since these compounds are readily available in planktonic and other biotic communities. Lipids are also considered to be the most important sparing compounds. By adding 5% of soyabean oil the optimum protein requirement of young mirror carp can be brought down to 33% from 38%. The addition increases the dietary metabolized energy from 2.8 to 3.1 Kcal/g.
Vitamins: Studies on vitamin requirements of fish are very limited. The values of quantitative requirements of vitamins in common carp and the symptoms of their major deficiencies are presented in Table 15.
| Vitamin | Requirement (mg/kg diet) | Major vitamin deficiency symptoms |
|---|---|---|
| Thiamin | Na | Nervousness and fading of body colour. |
| Riboflavin | 7.0 | Hemorrhages on skin, fin, mortality |
| Pyridoxine | 5–6 | Nervous disorders |
| Pantothenic acid | 30–50 | Poor growth, anaemia, skin hemorrhages, exophthalmia |
| Nidcotinic acid | 28 | Hemorrhages on skin, mortality |
| Biotin | 1 | Poor growth |
| Folic acid | N | None detected |
| Vitamin B12 | N | None detected |
| Choline | 4 000 | Fatty liver |
| Inositol | 440 | Skin lesions |
| Ascorbic acid | Na | Impaired collagen formation |
| Vitamin A | 10 000 IU | Faded colour, exophthalmia, hemorrhages on fin and skin |
| Vitamin D | N | None detected |
| Vitamin E | 200–300 | Muscular dystrophy, mortality |
| Vitamin K | N | None detected |
N = No dietary requirement demonstrated under variousenvironmental condition.
Na = Not available
Minerals and trace elements: Like higher vertebrates, carps also have dietary requirements of minerals such as calcium, iron, magnesium and phosphorus and trace elements such as cobalt, iodine, zinc, copper, manganese, sulpher, fluorine, molybdenum, etc. For common carp the minimum requirement of phosphorus in the diet is 0.6–0.7% and that of calcium is about 0.028%. 1% dicalcium-phosphate is recommended in the feed for adult fish in polyculture system in ponds. Trace elements are growth stimulants and are required in traces. Sen and Chatterjee (1976, 1979) reported that cobalt chloride and manganese at the rate of 0.01 mg/day/fish gives higher rates of survival and growth of spawn, fry and fingerlings of Indian major carps. Rohu requires about 0.014% dry diet of iron. In general, carps appear to be less sensitive to mineral deficient diets than other fish possibly due to meeting their dietary mineral requirements from natural sources under pond culture condition.
Common feedstuffs: A large number of feed stuffs are presently being used as supplementary feed for carps in undrainable pond culture systems. Some of them are widely available and extensively used. These may be broadly classified into two groups: the feeds of plant origin and the feedstuffs of animal origin.
Cakes of oil seeds such as groundnut, mustard, linseed, coconut, etc., are a most useful and widely used feedstuff of plant origin with high fat and protein contents. Brans of rice, wheat and other grains are equally popular and used in combination with oil cakes. Such meal as soya waste after oil extraction is excellent feed for carps. Broken cereals such as rice, wheat, maize, etc., are good but expensive feed materials. Leafy feeds are suitable for grass carp. Tender leaves of various aquatic and terrestrial plants (cassava, maioc, colocasia, banana, sweet potatoes, maize, etc.) and green animal fodder such as berseem, napier, paranapier, elephant grass, etc., are also used. Miscellaneous items such as kitchen wastes, household scraps, residues of bakery, beer brewing or rice-wine industry wastes can be profitably used as fish feed.
Dried fish meal (fish flour) is the most common and cheapest source of animal protein and widely used in livestock and fish feeds. Slaughterhouse offals, prawn head meal, bone meal, silkworm pupae and items like snails, oligochaete worms, etc., are also widely used depending on their availability and price. Nutritive values of some commonly used feedstuffs are presented in Table 16.
Digestibility and absorption greatly vary with the quality of the feedstuffs and also from fish to fish. The values of total digestible nutrients in common feedstuffs are given in Table 17.
| As percentage of dry matter | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Common name | DM | CP | EE | CF | Ash | NFE | Ca | P | Methioine & czstine | Lysine | Digestible energy K cal/kg |
||
| A. | Plant product | ||||||||||||
| Groundnut oil cake | 94.0 | 40.1 | 12.2 | 14.0 | 7.8 | 25.9 | - | - | 0.52 | 1.44 | 3 018 | ||
| Groundnut oil meal | 89.7 | 37.3 | 0.3 | 6.2 | 3.0 | 35.7 | 0.22 | 0.75 | 0.48 | 1.34 | 2 155 | ||
| Coconut oil cake | 92.3 | 18.1 | 8.9 | 16.4 | 4.6 | 52.0 | 0.21 | 0.58 | 0.34 | 0.45 | 2 960 | ||
| Soyabean cake | 84.8 | 47.5 | 6.4 | 5.1 | 6.4 | 34.6 | 0.13 | 0.69 | 1.42 | 2.90 | 3 009 | ||
| Soyabean oil meal | 88.7 | 52.8 | 1.5 | 6.6 | 7.6 | 46.7 | - | - | 1.58 | 3.22 | 3 060 | ||
| Cotton seed oil cake | 87.9 | 26.4 | 5.7 | 24.2 | 6.6 | 37.1 | - | - | 0.74 | 1.08 | 2 572 | ||
| Sunflower oil cake | 91.0 | 34.2 | 14.3 | 13.2 | 6.6 | 31.8 | 0.30 | 1.30 | 1.36 | 1.19 | 3 394 | ||
| Sunflower oil meal | 90.0 | 42.7 | 4.0 | 16.1 | 7.7 | 29.5 | - | - | 1.70 | 1.49 | 2 827 | ||
| Linseed oil cake | - | 30.5 | 6.6 | 9.5 | 10.2 | 43.2 | 0.37 | 0.96 | 1.34 | 1.07 | 2 983 | ||
| Sesame oil cake | 90.0 | 32.2 | 14.4 | 20.3 | 11.1 | 22.0 | - | - | 1.64 | 0.93 | 3 035 | ||
| Ground maize | 89.6 | 5.1 | 8.7 | 3.9 | 1.1 | 81.2 | - | - | 0.10 | 0.12 | 3 326 | ||
| Wheat bran | 90.7 | 13.9 | 8.3 | 13.1 | 4.6 | 60.1 | - | - | 0.42 | 0.53 | 2 995 | ||
| Rice bran | 91.3 | 13.7 | 5.4 | 20.0 | 18.1 | 48.8 | - | - | 0.52 | 0.56 | 2 416 | ||
| Rice polish | 91.6 | 12.4 | 16.7 | 12.0 | 14.1 | 44.9 | - | - | 0.73 | 0.78 | 3 154 | ||
| Millet | 88.4 | 12.0 | 4.8 | 11.3 | 5.0 | 66.9 | 0.57 | 3.21 | 0.36 | 0.43 | 2 847 | ||
| Black gram bran | 88.8 | 7.0 | 3.6 | 24.0 | 8.9 | 56.5 | - | - | 0.12 | 0.51 | 1 684 | ||
| B. | Animal products | ||||||||||||
| Blood meal | 89.5 | 88.5 | 1.2 | 0.4 | 6.0 | 3.9 | 0.28 | 0.28 | 1.95 | 7.08 | 3 576 | ||
| Bone meal | 75.0 | 36.0 | 4.0 | 3.0 | 49.0 | 8.0 | 22.0 | 10.0 | 0.25 | 1.69 | 2 000 | ||
| Fish meal | 86.0 | 55.6 | 12.0 | 2.9 | 21.3 | 8.2 | - | - | - | - | 3 569 | ||
| Prawn meal | 89.4 | 31.2 | 11.7 | 17.6 | 39.5 | 0.0 | - | - | - | - | - | ||
| Silk worm pupae | 20.0 | 54.2 | 30.3 | 3.9 | 5.2 | 6.4 | 0.1 | 1.1 | - | - | 4 910 | ||
| Fresh cattle manure | 17.9 | 8.4 | 3.1 | 22.5 | 18.8 | 47.2 | - | - | - | - | 1 983 | ||
DM - Dry matter;
CP - Crude protein;
EE - Ether extract;
CF - Crude fibre;
NFE - Nitrogen free extract;
CA - Calcium;
P - Total phosphorus.
Usually the crude protein level of the supplementary feed is fixed at about 5 to 10% below the dietry protein requirement of the fish to be fed. Vitamins, minerals and trace elements are added as required.
| Feedstuff | Digestible nutrients (%) |
|---|---|
| Coconut oil cake | 67.5 – 69.8 |
| Ground nuts | 79.3 |
| Rice bran | 79.4 |
| Maize (Corn) | 77.9 |
| Maize (fresh) | 74.9 – 75.1 |
| Rye | 75.9 |
| Sweet potato | 25.8 |
| Radish leaves | 8.2 |
| Fresh silkworm pupae | 34.3 |
Formulation of feed: Easy availability, low cost, high digestibility and high nutrient contents are the major considerations in selecting the fish feed ingredients for feed formulation. Feed constitute the major operating cost in undrainable pond fish culture and therefore, our ultimate objective is to supply essential nutrients at the minimum possible cost. Formulated feeds may be either a complete feed with optimum level of all the essential nutrients and energy to provide complete nutrition or a supplementary feed - a diet basically to supplement energy and a portion of protein and other essential nutrients. In undrainable pond culture systems where natural feed are made available by pond fertilization, feed is required only to supplement the natural feed. The initial step involves surveying market prices of the locally available feedstuffs and tabulation of data as mentioned below as an example (Table 18).
| Feedstuff | Market price (US $/kg) | Protein content | Cost/kg protein | Grade for selection (US $) |
|---|---|---|---|---|
| Groundnut oil cake | 0.15 | 38.2 | 0.39 | II |
| Mustard oil cake | 0.21 | 40 | 0.52 | III |
| Sesame oil cake | 0.11 | 32.2 | 0.34 | I |
Thus, out of the three listed above one can easily select the feedstuff most suitable for his operation. Similar methods may be adopted to find the best possible feed for the supply of specific major nutrients. Their amino acid profile is also to be considered for such selection. Using the locally available feedstuff, a diet with desired level of protein can easily be formulated by using the square method. The same method is also used for adjusting energy levels in a feed.
The required protein level of 30%, for example, is put in the centre of the square. The two selected feedstuffs with their percentage of protein content are put on the left hand corners of the square as shown below.
| Sesame oil cake(Protein 32.3%) | 30—10 = 20 | |
| Desired feed protein level(30%) | ||
| Rice bran(Protein 10%) | 32.2—30 = 2.3Total 22.3 |
The value of desired protein level of the proposed feed is substracted from each of the feedstuffs in turn and the results are placed at the opposite corner ignoring the resultant positive or negative signs. The two resultant figures on the right hand side of the square are then added together (20 + 2.3 = 22.3). Now to obtain 30% crude protein level in the proposed feed, the following formula is followed.
Thus, to obtain 30% crude protein level in 100 kg of feed we need 89.6 kg of sesame seed cake and 10.3 kg of rice bran to be mixed together. The same method can also be used to obtain a desired dietary energy level. It has been experienced that if the minimum dietary requirements for amino acid like arginine, lysine, methionine and tryptophan are met, the requirements of 6 other essential amino acids usually also get satisfied. Vitamins, minerals and trace elements are added in feed according to the requirements of the species of carps under culture.
Pelletization: Considerable wastage is expected when supplementary feed mixtures rapidly separate into their component ingredients during the feeding process. However, by pelletization of supplementary feed mixture, such wastage can be minimised and further improvement in the feed efficiency can be achieved. Feed in pellet forms are more readily acceptable and give better results in comparison with dust feed (Kumar et al., 1984). During pelletization, the soft and dusty feed is converted into hard, water-stable pellets by the process of heating and compression. Even in undrainable ponds use of supplementary feed in pelleted form promise increased production through increased efficiency and minimum wastage (Figs. 33A and 33B).
Figure 33A. Fish Feed in Dough Form
Figure 33B. Fish Feed in Pelleted Form
A generalised but practical account of nutrient specifications of commercial warm water aquaculture feed is given in Table 19a.
| Nutrients | Fry and fingerlings | Juveniles and adults | Brood Fish |
|---|---|---|---|
| Protein (% min) | 30 | 25 | 30 |
| Lipids (% min) | 8 | 5 | 5 |
| Ca (% min) | 0.8 | 0.5 | 0.8 |
| Ca (% max) | 1.5 | 1.8 | 1.5 |
| P (% min) | 0.6 | 0.5 | 0.6 |
| P (% max) | 1.0 | 1.0 | 1.0 |
| Lysine (% min) | 2.0 | 1.6 | 1.8 |
| Digestible | |||
| Energy (KcaL/100 g min) | 310 | 280 | 280 |
| Vitamins (Supplement), | (per 100 kg) | ||
| A (i.u.) | 600 000 | 500 000 | 600 000 |
| D (i.u.) | 100 000 | 100 000 | 100 000 |
| E (i.u.) | 6 000 | 5 000 | 6 000 |
| K (g) | 1.2 | 1.0 | 1.0 |
| C (g) | 24.0 | 20.0 | 24.0 |
| Thiamine (g) | 2.4 | 2.0 | 2.4 |
| Riboflavin (g) | 2.4 | 2.0 | 2.4 |
| Pantothenic acid (g) | 6.0 | 5.0 | 6.0 |
| Niacin (g) | 12.0 | 10.0 | 12.0 |
| Pyridoxine (g) | 2.4 | 2.0 | 2.4 |
| Biotin (g) | 0.024 | 0.020 | 0.024 |
| Folic Acid (g) | 0.6 | 0.5 | 0.6 |
| Choline (g) | 54.0 | 50.0 | 54.0 |
| B-12 (mg) | 2.4 | 2.0 | 2.4 |
| Minerals (Supplement), | (per 100 kg feed) | ||
| Iron (g) | 5.0 | 5.0 | 5.0 |
| Copper (g) | 0.3 | 0.3 | 0.3 |
| Manganese (g) | 2.0 | 2.0 | 2.0 |
| Zinc (g) | 3.0 | 3.0 | 3.0 |
| Iodine (mg) | 10.0 | 10.0 | 10.0 |
| Cobalt (mg) | 1.0 | 1.0 | 1.0 |
| Selenium (mg) | 10.0 | 10.0 | 10.0 |
Based upon the nutrient specifications, a number of test diets for carp fry, fingerling and brood fish are under extensive trials to determine which would be the preferred formulations in terms of efficiency and cost.
The conventional rice-bran and oil cake mixture lacks animal protein, minerals and vitamins and rapidly separates into its component ingredients during the feeding process. Considerable improvement is possible if this conventional rice-bran and oil cake mixture is simply fortified with 15–25% fish meal, 0.1% mineral mixture, 0.1% vitamin mixture and pelletized. Although mineral and vitamin mixtures are commercially available as common additive of animal feed, fish meal at a reasonable price may not be easily available in rural areas.
Considerable quantities of nutrient elements are regularly removed from the pond ecosystem through the harvested fish crops and thus for retaining the pond fertility, the required amount of nutrients need to be replenished. These nutrients are broadly divided into two groups. The first group of nutrients are nitrogen, phosphorus, potassium, carbon and calcium, while the second group of nutrients which are needed in very minute quantities constitute mainly copper, zinc, iron, manganese, cobalt, boron, molybdenum, etc. It is the first group of nutrients which are more concerned with pond fertility in terms of primary production, consumed in more quantity and thus need to be compensated from outside in the form of fertilizers. In other words, the main objective of adding fertilizers in fish ponds is to maintain a sustained production of natural fish food during the entire culture period. Fertilizers are also classified into two categories: inorganic fertilizers or mineral fertilizers and organic fertilizers or manures of plant and animal origin.
Organic manures have been in use in fish culture in India and the Far East countries for a long time. They are available in a variety of forms such as dung of cattle, sheep, pig and goat, poultry droppings; de-oiled cakes of mahua, mustard, castor, linseed, neem, etc. They also come in the form of farmyard manure, compost, green manures, sewage, etc. Of these, cow dung is the most widely used manure in undrainable pond culture system. Most of the organic manures are by-products of local agriculture, animal husbandry and village based agro-industrial activities and hence their procurement is relatively easy at low cost. They are composite in nature and provide practically all the nutrients, including organic carbon, required for biological production. Several organic manures are immediately assimilated by the aquatic fauna and especially by the zooplankton or even by some species of cultured carps. By improving the quality of the pond bottom mud they encourage bacterial growth which in turn favours better production of zooplankton and also through inducing increased bacterial decomposition help in releasing mineral constituents of the soil into the water. It also increases the effectiveness of many inorganic fertilizers by providing the necessary organic matter base. Though the presence of the major nutrient elements in these manures is rather at a lower level and often vary quantitatively, their effect is sustained over a longer period. However, they are required in large quantities, thereby making the procurement, transport and application somewhat troublesome and costly though the manure itself is cheap. Also, unless proper care is exercised in its use, depletion of dissolved oxygen, in the pond water is likely to occur with consequent loss of fish by asphyxiation. However, better yields of fish are obtained through a judicious manuring schedule.
Commercially produced inorganic compounds containing major nutrients - nitrogen, phosphorus and potassium are known as inorganic or chemical fertilizers. They contain a high and fixed percentage of one or more major nutrients depending on the class (nitrogenous, phosphatic, potassic or mixed) of fertilizer. Due to their high solubility in water, the nutrients become readily available soon after their application. Some fertilizers are also available in liquid form which offer several advantages over the conventional granular or powdered form of fertilizers.
8.3.2.1 Nitrogenous fertilizers
Nitrogenous fertilizers usually contain nitrogen as the principal element and are commercially available as ammonium sulphate, ammonium nitrate, urea, etc. Most of the nitrogenous fertilizers deplete reserves of bases and make soil acid. Therefore, the form of nitrogenous fertilizers may be selected on the basis of acidity, neutrality or alkalinity of the soil type (Saha, 1969). Nitrogenous fertilizers are particularly essential for newly constructed ponds which are poor in nitrogen and do not have sufficient organic matter in its bottom, whereas older ponds having a good layer of colloidal mud are capable of producing nitrogen by itself. Further, the efficacy of nitrogenous fertilizers is inhibited by phosphorous deficit. It is best to maintain the P/N ratio at 1/4.
8.3.2.2 Phosphatic fertilizers
Phosphatic fertilizers are by far the most effective and favourable for fish culture. It is all the more important because almost all fish ponds exhibit phosphorus deficiency. The most commonly used phosphatic fertilizers are the orthophosphates and are grouped roughly according to their solubility in water. Superphosphates are the most soluble in water, dicalcium phosphate is partially soluble and rock phosphorus is almost insoluble in water. Amongst the phosphatic fertilizers, single superphosphate is extensively used and is easily available. The more concentrated triple superphosphate is also in use which has P2O5 (Phosphorus pentaoxide) equivalent up to 45% with 85% solubility and thus involved relatively lower transport cost. Generally, the phosphatic fertilizers are held in soil and liberated gradually with the result that its action is extended to subsequent years of its application, mostly depending on the nature of the pond bottom.
8.3.2.3 Potassic fertilizers
Although potassium ranks as a major nutrient like nitrogen and phosphorus, its importance in pond fertilization is less pronounced since it is available in a required quantity in natural waters. Muriate of potash (Kcl) and sulphate of potash (K2SO4) are the two commonly used fertilizers as a source of potassium. The favourable action of potassic fertilizers can be seen in ponds with low alkalinity, with peaty bottoms. In general, for ponds in which phytoplankton production is rather slow, potassic fertilizers may be tried. It also improves the hygienic conditions of fish ponds, particularly the rearing ponds.
8.3.2.4 Calcium
Though calcium is not considered as a nutrient to be used as fertilizer, it is another integral part of the ecosystem and is usually applied to get the benefit of added fertilizers used in a pond. In ponds where the water is poor in calcium (less than 8 mg Cao/1), the freshwater flora, molluscs and crustaceans are either rare or absent which in turn diminishes the nutritive value of the water. Calcium present in required quantities also neutralises the harmful action of excessive magnesium, sodium and potassium salts. It is usually applied in the form of lime, which is widely available as ground lime stone (CaCo3), slaked lime (Ca(OH)2) and quick lime (Cao). Composition of some important manures and inorganic fertilizers commonly used in pond culture are listed in Table 19b.
Procurement of organic and inorganic fertilizers is relatively easier than other essential inputs like feed and seed. Organic manures are locally available and in most cases they are available within the community. However, due to extensive adoption of intensive crop farming there is a growing demand for animal manure or compost in agriculture. Instead of procuring the whole lot of required manures at a time and storing them for application over extended periods, it is always convenient and desirable to procure materials in small quantities and apply them as and when required. While storing the manure, it should be covered to protect it from direct sunlight. Inorganic fertilizers being extensively used as an agricultural input, the listed fertilizers (Table 19b) are easily available in the local markets. Prolonged storage, high humidity, etc., cause deterioration in the quality of inorganic fertilizers and hence only a specified quantity of materials required for 2-3 months should be procured at a time. Selection of fertilizers depends mainly on their nutrient content, cost and suitability for the specific soil condition.
| Items | Nutrient content (%) | ||||
|---|---|---|---|---|---|
| Nitrogen (N) | Phosphate as Phosphoric (acid(P205) | Potassium as Podtash (K20) | |||
| Fresh excreta of animals: | |||||
| Cow | 0.60 | 0.16 | 0.45 | ||
| Sheep | 0.95 | 0.35 | 1.00 | ||
| Pig | 0.60 | 0.45 | 0.50 | ||
| Duck | 1.00 | 1.40 | 0.62 | ||
| Hen | 1.60 | 1.5 – 2.00 | 0.8 – 0.9 | ||
| Deoiled cakes: | |||||
| Mustard | 4.5 | 2.0 | 1.0 | ||
| Groundnut | 7.8 | 1.5 | 1.3 | ||
| Mohua | 2.5 | 0.8 | 1.8 | ||
| Others: | |||||
| Farmyard manure | 0.5 – 1.5 | 0.4 – 0.8 | 0.5 – 1.9 | ||
| Compost | 0.4 – 0.8 | 0.3 – 0.6 | 0.7 – 1.0 | ||
| Green manure | 0.5 – 0.7 | 0.1 – 0.2 | 0.4 – 0.8 | ||
| Inorganic fertilizers: | |||||
| Nitrogenous - | |||||
| Ammonium sulphate | 20.5 | - | - | ||
| Urea | 43–45 | - | - | ||
| Ammonium nitrate | 20.5 | - | - | ||
| Sodium nitrate | 16.0 | - | - | ||
| Phosphate: | |||||
| Single superphosphate | - | 16.0–20.0 | - | ||
| Triple superphosphate | - | 40.0–45.0 | - | ||
| Potassic: | |||||
| Muriate of potash | - | - | 48.0–62.0 | ||
| Sulphate of potash | - | - | 47.0–50.0 | ||
