3. CULTURE TECHNIQUES

3.1 General considerations

Various production conditions can be found in Bangladesh. It seems that African magur can be adopted to these wide range of possibilities. However, intensity of production depends on the following parameters:

• Pond size - Most of the small ponds around the farm are suitable for magur stocking after some modifications. But the large, more than 1 acre undrainable ponds are not recommended for stocking with African magur. For large scale production properly designed ponds should be constructed.

• Availability of fingerlings - Year-round, multi-crop culture of African magur largely depends on availability of fingerlings throughout the year. Under the local conditions of Bangladesh, it is now possible to breed magur for at least 8 months in a year.

• Availability of inputs - The input demand increases exponentially with the intensity of production. But in small-scale culture where magur, is a small component in polyculture, the input cost is little. With the increase in intensity of production the input costs rise sharply.

• Availability of feed ingredients - For African magur culture, the protein feed supply is the main limiting factor. One should find out first where the slaughterhouse by-products or other cheap animal protein sources are available on a daily basis and in adequate quantities.

• Marketing - The present market system (mainly in rural areas) is favourable to small scale operations. When the production of African magur is specialized and intensified, the market channel should be found out before stocking of fingerlings. For commercial production of magur, detailed market study should be carried out before embarking on such operations.

3.2 Preparing pond for magur production

Construction of new ponds

Before deciding to construct a new pond for magur culture the followings should be checked:

• that the area is flood free even at the highest flood level;

• that the water retention capacity of the soil is good. Soil type should be checked first. Pond construction on sandy soil is not at all recommended.

The suitability of soil can be tested by an easy method:

Dig a 1–1.2 m (3ft – 4ft) hole on the proposed site and fill the hole with water. Next day fill again to make up the water loss by seepage. After 24 hours the water level and the wall should be checked. If the wall do not collapse and the water level remain more or less same the soil is suitable for magur pond.

While making embankments, roots, leaves and other organic particles should be removed from the soil, and the soil should be compacted well. Local traditions and low initial input demands support the simple undrainable ponds. But wherever the topographical conditions allow, construction of an outlet monk is highly recommended. Permanent construction of water inlets and outlets facilities like monk is more economic in long run.

The pond bottom should be prepared flat with slight slope to the outlet or the usual pumping place. Grass should be planted on the top and the slopes of dykes to reduce erosion.

Repairing existing ponds for magur culture

In most cases existing ponds can be converted for African magur monoculture or polyculture. For polyculture of magur with carp species, the pond should be such that all the magur could be harvested at the end of each production cycle. Otherwise, left over mature magur may prey upon carp fingerlings stocked for subsequent production cycles. To avoid this problem, the following steps should be taken --

1. Make the pond bottom flat to ensure complete netting
2. Increase the height of dykes if there is danger of flooding
3. Repair eroded parts of dykes and seal water leakage/seepage.

Eradication of undesirable fishes

Before stocking fingerlings in the pond it is necessary to eradicate the unwanted fish from the pond. Predator and weed fish tend to decrease yield considerably. Repeated netting may not be sufficient. It is, therefore, necessary to apply fish toxicants. Some of the efficient toxicants listed below can be used:

Rotenone

Rotenone kills all fish species except shrimps when applied @2–3 ppm. The killed fish is also suitable for human consumption. However, rotenone is expensive and not easily available.

Phostoxin

This is a kind of fumigant poison found in tablet form specially prepared for control of storage pests. Active ingredient is Aluminium phosphide (57%). Phostoxin has been found very effective in killing all sorts of fish @0.2 ppm. Toxicity lasts for around 10–15 days. The killed fish is also fit for human consumption.

Tea seed cake

In tea seed cake the active ingredient responsible for killing fish is the Saponin. Tea seed cake is effective at 75–100 ppm. (5 – 10 ppm Saponin content). The toxicity lasts for about 10–12 days and the killed fish is fit for human consumption. Tea seed cake is easily available in Sylhet and Chittagong Districts.

Mahua oil cake

Mahua (Basia latifolia) oil cake contains 4–6% Saponin and kill fishes when applied @ 250 ppm. The toxicity lasts for about 10–15 days under normal conditions. Killed fish is fit for human consumption. It also serves the purpose of base manure in the pond.

Bleaching Powder

Calcium hypochlorite [CaOCl₃], as fish toxicant has been found to kill fishes within 3–4 hours when applied @ 30 ppm. Its toxicity lasts for about 7–8 days in the pond. Killed fish is not fit for human consumption. It kills all sorts of biota in the pond. Repeated use may cause the reduction of pond productivity.

This chemical has an excellent disinfecting effect besides oxidizing the decomposing matter on the pond bottom.

Dose calculation

For calculating the actual quantity of piscicide required for a particular pond the following formula can be used :

Liming

Liming of a fish pond is highly recommended if the soil is not alkaline. Lime neutralizes soil acidity and creates a buffer system to prevent marked diurnal changes of the water from acidic to alkaline conditions. Apart from other advantages, this buffering action of calcium is the most important. Lime treatment for ponds should be done before initial manuring as follows (Table II):

Table II: Quantity of lime required for different soil types

(Adapted from Kumar MS)

For treating the pond bottom after dewatering, the quick lime [CaO] is the best. Application of quick lime @30–40 kg per bigha also disinfects the pond to some extent. For water treatment only the slacked lime [Ca(OH)2] should be used instead of calcium oxide.

Initial fertilization

A well prepared zooplankton-rich water is the best starter for magur fingerlings. The magur fingerlings try to supplement its higher protein requirement from natural sources. At stocking when the size is 2–3 cm, the bigger size zooplankton (e.g. Cladocera sp., Diaptomus) is the cheapest and best food source for fingerlings.

In different types of magur culture in earthen ponds considerable quantities of nutrient elements are removed from the pond ecosystem through fish production. Therefore the fertilizer requirements vary among different soil productivity levels and the intensity of production. Organic manuring besides being important as means of adding the nutrients is also equally important for improving the soil texture. During the shortage of organic manures, application of inorganic fertilizers is recommended. In absence of chemical testing of water and soil of ponds the generally recommended fertilizer schedule as in Table III may, however, be adopted with expectation of moderate results.

Table III Generally recommended initial fertilization

* In case of magur monoculture half the quantity of Urea and TSP may be enough.

Programming of pond preparation

Before starting pond preparation one has to fix the time of delivery of fingerling from the hatchery for stocking. All preparations should be finished 5–7 days before the stocking date. With too early pond preparation (above 2 weeks) the advantages of zooplankton may be lost. Pond preparation schedule as described in Table IV may be followed.

Table IV: Schedule of Pond Preparation

Note: If the pond is not poisoned, fingerlings can be stocked on 10–12th day

3.3 African Magur dominated polyculture

In this combination the magur is the main species. Other supplementary species are used for pond utilization of natural feed in the pond and to help maintain water quality. For magur dominated polyculture with carp species, semi-intensive culture system should be practised.

Supplementary species

Silver carp (Hypophthalmichthys molitrix). This seems to be an ideal species with African magur. There is no feed competition between the two species. Silver carp utilize the phytoplankton and small size zooplankton (Rotifers) which magur does not consume. Another advantage of silver carp is that with its water filtering activity the danger of algal bloom decreases and the water quality improves.

Catla (Catla catla). This is the fastest growing Indian major carp, a native of Bangladesh and is a surface feeder like silver carp. Catla is predominantly zooplankton feeder but occasionally consume some phytoplankton, smaller floating feed particles and decaying macro-vegetation.

Grass carp (Ctenopharyngodon idella). Typical herbivorous species, consuming all sorts of aquatic and terrestrial vegetation. Small number of grass carp can be stocked to keep the pond clean from vegetation and utilize the grass growing on embankment. 50 pieces of grass carp is sufficient to control aquatic weeds in 1 bigha pond.

Stocking of pond

The fry and fingerling can be transported from nurseries when the pond is ready for stocking. The following things should be checked on receipt of magur fry:

1. The fry is ready for stocking when the arborescent organs are developed. It is completed after about two weeks of age. It is easy to identify by the special behavior of air gulping. The small magur fry vertically swims up to the surface to breathe air and quickly goes down.

2. Size of fingerlings should be equal. Size differences in magur naturally occur from the beginning of rearing. Fingerlings of equal size should be sorted out from the stock. The fingerlings may be kept in a net for a short time, the mesh size of which will allow the small ones swim out. The bigger size fingerlings should be picked up by hand during counting. The initial size differences will be even more during the grow-out period and that difference creates problems like cannibalism.

3. Check the health condition of the fingerlings. Only healthy fingerlings should be stocked. The following signs would help in identifying the healthy from the unhealthy fingerlings.

   Healthy magur fingerlings

   • quick moving and gathering on the bottom of the net;
   • fast swimming up and down when gulping air;
   • unbroken barbels and fins;
   • skin is uniformly dark-grey colour covered with mucus.

   Unhealthy magur fingerlings

   • The fingerlings hang vertically on the surface with weak response to disturbances;
   • Barbels and fins are broken;
   • Big, white-grey spots, without mucus, on the body surface.

For short distance transportation magur fry can be transported in plastic buckets with led. For long distance transportation, plastic bags with oxygen should be used. For this, the fingerlings should be held in a hapa for 12 hours to get their guts cleared. Otherwise, decaying faeces in the water inside the plastic bag produces ammonia which may cause high mortality during long distance transportation. Before releasing in the pond, the fingerlings should be acclimatized to the temperature of the pond water. This can be done by slowly adding pond water into the water containing the fingerlings inside the plastic bag.

The stocking rate of magur and the supplementary carp species will vary according to (i) the availability of feed for magur and (ii) the pond conditions, especially on the quantity and the quantity of natural feed present in the pond. However, the following stocking rate (Table V) is recommended for semi-intensive magur dominated polyculture system.

Table V: Stocking details in magur dominated polyculture system

* Optional

Feed

In semi-intensive production level the growth of magur is highly dependent on the quality and quantity of supplementary feed. As the stocking rate in the pond increases the feed requirement also increases. Protein is the most expensive component of the magur supplementary feed and is the most important nutrient in the diet. Protein sources should be first identified from the ingredients available within reasonable distance. In semi-intensive pond culture most of the protein demand must be met through the supplementary feed. Smaller part is gathered by the fish from the well prepared pond water. Only a small part of the protein requirement may be met from the natural feed available in the pond. The basic level of nutrient requirement of African magur is given in Table VI.

Table VI: Nutrient requirement of African magur (Modified after Janssen 1987)

The chemical composition of the easily available magur feed ingredients are shown in the Table VII.

The above mentioned requirements can be maintained from limited sources in the country. There are some ingredients which are generally available and suitable for semi-intensive magur production (Table VII).

Table VII: Chemical composition of generally available ingredients for magur feed (as % of dry matter) (Modified after New, 1987)

The price of feed is a determining factor in the cost of production. Above 1 fish/m² stocking rate the cost of feed is the major expenditure determining the profitability of magur culture. Therefore the cheapest suitable and available ingredients should be chosen. In small scale production, slaughter house by-products such as cattle and goat blood, poultry and other animal viscera etc. are recommended for use instead of fish meal.

The advantages of slaughter house by-products are cheap price and good quality protein, as shown in the example below:

The main disadvantages of slaughter house by-products are --

• limited availability in rural areas;
• not available every day in smaller villages and towns;
• it needs daily collection.

Magur feed can be prepared following the formulae given below:

Magur feed formula for semi-intensive conditions

Feed preparation

Feed should be prepared daily. In the morning, total amount of feed for the day should be prepared. When the magur size is below 100 g the viscera should be minced with the hand grinder. However, Chopping to 1–2 cm size is sufficient for bigger fish. Mix the ingredients thoroughly and shape the feed into balls or pie form. In case of uncertainty in daily supply of slaughter house by-products, home made feed pellet prepared in dry season can be reserved for some days.

Preparation of pellet: Mix the ingredients as mentioned above and make pellets with hand grinder or small grinder machine at morning time. Then sun dry it (3–4 mm diameter pellet) until evening. The dry mixture is usable for 2–4 days with proper storage.

Feed ration and feeding technique

To maintain the proper growth rate of magur daily feeding is necessary. The average size by weight and the estimated total biomass of the magur population in the pond are the basis for determining the total daily ration requirement. A general guideline for daily feeding rate of magur in water temperature above 24°C is given in Table VIII. Following this guideline the daily ration required for magur in a pond can be calculated as follows:

Table VIII: Guideline for feeding rate of African magur

1. Average body weight of magur = 10 g
2. Estimated total no. of magur in the pond = 1500
3. Total biomass in the pond = a × b= 10 × 1500 = 15000 g = 15 kg
4. Daily ration for magur of average size 10 g = 30% of body weight
5. Total daily ration required for a magur biomass of 15 kg
   

Below 24°C water temperature the appetite of magur decreases and under 19°C they practically stop eating.

To avoid over feeding - which may cause water quality problems with its consequences and unnecessary cost - feed checking is highly recommended. If left over feed is found in the feeding places after one hour of feeding, the daily quantity should be reduced and adjusted.

Feed should be given 2 or 3 times a day at equal intervals (for example 8 AM, 12 PM, 4 PM), and in equal amount.

At the beginning of the growing period (1–2 weeks) it is suggested that feeding trays be used to control feeding in certain areas only. If the feed is consumed within 10 minutes, 5–10% increase is recommended. Later on, feed can be placed in show waters in the four corners of the pond. It is better to feed in the same area of the pond and the fish fed used to the feeding areas very soon.

3.4 Magur cum poultry integrated system

Background and benefits of the culture method

The digestive tract of a chicken is very short, only 6 times its body length. Therefore, part of the eaten foodstuff are defecated by the chicken before being fully digested. Research has shown that about 80 percent (by dry weight) of feedstuff is utilized and digested by the chicken, leaving 20 percent for use by the fish the integrated fish culture system. Chickens also peck at their food, causing 10–15 percent of the feed to be scattered over the feeding ground. This wasted feed can be utilized directly by fish. The total protein content of dry chicken excrement can be as high as 30 percent. In general, a good chicken feed has a protein content over 18 percent (Table IX).

Table IX: Composition (%) of chicken manure (dry) of from different chicken-raising methods.

Source: Adapted from NACA. 1989.

When magur culture is integrated with chicken raising in chicken house built on the pond water surface, the following advantages can be gained --

• direct discharge of fresh chicken manure to the fish ponds produces enough natural fish food organisms without any additional fertilization of the pond water.

• transportation cost of the manure is also eliminated.

• value of applied fresh manure is much higher than the dry manure mixed with saw dust.

• parts of the manure is consumed directly by the fish.

• no or very little supplementary feed is needed for the fish.

• better space utilization is achieved by constructing chicken sheds over the pond water.

• More production of valuable animal protein (fish/chicken/eggs) from the same surface area.

Magur sub-system:

The magur sub-system under the magur-cum-chicken integrated system in described below:

Pond size: 500–1500 m²
Depth     : 1.5–1.8 m

Stocking details of African magur and other compatible carps are given in Table X.

Table X: Stocking rate of magur and other carps (fingerlings/bigha)

Culture period: 3 months (200–300 g marketable size)

Expected production of magur:

Under magur-cum-chicken integrated semi-intensive system, the expected magur production is summarized below:

Supplementary feed

The supplementary feed composition is same as described in section 3.3. However, the quantity of feed required depends upon the number of chicken being integrated and the stocking density of magur. The actual feeding rate should be calculated always by the magur culturist, considering the growth rate of magur, the estimated total biomass of magur and the amount of waste-feed and excrement being contributed by the chicken sub-system.

Under the ‘without feeding’ system, the growth rate of magur should be checked at the interval of 7 days. After a period of 2 months some of the magur will reach the marketable size of 200–300 g, which should be selectively harvested and sold, making more food available to the slower growing magur.

POULTRY SUB-SYSTEM

Selection of species:

First of all the farmer should decide whether he want to be involved in egg or meat production. Where the market chain is good for broiler he may prefer it over layers because broiler production can be programmed within a shorter pond culture period (3–4 months). On the other hand, egg production of layer chickens can start only after six months of rearing of a day old chick. In Bangladesh, the layer or broiler is determined by the location of the farm. In Dhaka and Chittagong area, both the broiler and layer chicken are recommended for the sub-system as there are fairly good market for both chicken eggs and meat. In the country side only layer chicken is suggested because of limited market for broiler chicken.

At present the chicks of a number of varieties of poultry are available all over the country at Government Poultry Farms as well as private farms. But to meet special demands for integration with fish culture, mostly in small scale, only few of them are suitable. The most suitable varieties for integrated fish-cum-chicken system are mentioned in Table XI.

Table XI: Recommended poultry varieties for integration with fish culture

Chicken house/shed birds

Chicken sheds can be constructed out of locally available materials such as bamboo, wood, tin, etc. The size depends on the number and type of chicken. Floor space, nests, ventilation, temperature regulating device, dryness, light and sanitation are the main features to be considered for shed construction. Generally under local condition 10–12 broiler/m2 and 7–8 layer hen/m² are suggested.

The shed should be well constructed and be durable. The life time of a shed should be at least 3 years. Otherwise continuous repairing may need more cost than a new house. To extend the life time of bamboo water proof painting of the main support structures (legs), which would remain under water, is recommended.

Calculating the number of chicken for fish culture

In ponds without supplementary feeding, 120 – 150 birds/bigha water surface has been found suitable to maintain a satisfactory magur production. If water exchange facilities exist, more number of chicken could be integrated with magur culture.

Chicken feed and feeding technique

To achieve good production of eggs or meat the chicken should be fed with balanced diet. In Bangladesh suitable mixtures have been worked out which are used successfully by commercial chicken farms (Table XII).

The ingredients are available locally and can be mixed by the farmer. Some of the ingredients can be substituted (e.g til oil cake can be substituted by mustard oil cake) but the vitamin complex should not be changed or omitted. For small-scale operation of layer chicken rearing (50–200 birds), it is suggested that some additional feedstuff such as grass, crushed snail, kitchen waste etc. that are available from around the farm should be given.

Table XII: Suggested feed formula for layer and broiler chicken.

* Should be “A” quality.

In the case of sophisticated high production types the following feeding guidelines are suggested (Table XIII).

Table XIII Daily Ration guidelines for layer and broiler chicken.

Simple home made feeders and self-drinkers are suggested for use in the chicken house. The empty milk powder can (3–5) is excellent for self-drinker. Feeding twice a day is sufficient. Clean drinking water have to be made available near the feeders. Lack of water, besides quickly affecting egg production, can also cause dehydration, kidney damage and death. Polluted water causes health problems. To avoid parasitic infections, pond water should not be used as drinking water for the birds.

Day to day management

In integrated fish farming system usually smaller number of birds are used, making management easier though not simple. For maintaining good health of the birds and to ensure high production rate of eggs and meat the following important factors should be given special considerations.

Food and feeding

• Prepared feed, prepared in the farm be stored for two weeks in the dry season but not more than one week in the rainy season. Good storage of prepared feed and feed ingredients is very important (Fig.2). Decomposed or fungal infected feed must be avoided.

• Allow the chicken to graze for one hour a day at afternoon which is good for general health conditions of chicken and for maintaining higher percentage of quality egg production.

• The drinkers and feeders should be cleared everyday.

Fig. 2 Proper storage of feed stuffs

Lighting program

During the laying period, provision of some artificial light after sunset can increase the egg laying capacity by 15–20%. The use of artificial light should start from the time the layers are 150 days old. Starting with 30 minutes a day lighting should be increased by 30 minutes every week, until 16 hours of continuous illumination period is reached. This optimal duration should be maintained till the end of the laying period.

For broiler raising, 24 hours of lighting is recommended. In the absence of electricity supply, kerosene lamps should be used with precaution against fire.

Intensity and continuity of laying

Laying of eggs should start when the chicken reach 150–160 days. Optimum production period can be one year. After that the flock should be changed. Layer hybrids can reach 85–90 % laying rate at the beginning. Later on as the birds get older laying rate will decrease. With proper management a 62–65% laying rate could easily be achieved with the recommended species.

Ventilation

Climate in the rainy season remains too hot and humid, causing discomfort to the birds. As a result, egg laying goes down to 50–55%. Practically on farm level nothing can be done except maximizing the natural ventilation. Therefore, in the summer/rainy season, provision for additional ventilation in the chicken house should be made.

Brood stage

After laying certain number of eggs a hen may start to brood and stop laying eggs. This can be reversed by keeping the hen under light and by not allowing it to settle on a next. In much cases, the hens start laying eggs within a few days if they are kept looked in a small wire case.

Health

Every effort should be made to ensure good health of the birds. For this, quality of feed and the feeding programme must be maintained. The birds should be protected from stresses caused by charges in temperature, over-crowding, excessive noise etc. As a preventive measure strict programme of vaccination against common diseases must be followed. In Bangladesh, the following vaccination programme is recommended.

Broiler-Chicken

Layer-Chicken

3.5 African Magur and Carp polyculture

The African magur with its biological characteristics and feeding habit adopts well in a properly managed polyculture as a supplementary species.

One very important measure to be considered before stocking of this species is that all the magur should be removed from the pond after each production cycle. Left over big size magur can be dangerous for the fingerlings of a new production cycle.

In a properly managed fish pond, where the stocking size of African magur is half (or less) than the other species, the magur is not able to predate on other fish.

Stocking management

Stocking magur in low percentage (5–10%) of the total number of fingerling does not demand extra feeding but increases fish production and profit (price of magur is higher than carps).

A guideline for stocking is a 1 bigha, 1.8–2 m deep properly managed fish pond shown below (Table XIV).

Table XIV: Stocking combination of fish species (per bigha) in polyculture of carps and magur

Manuring:

In addition to, application of high dose of manure before stocking as described under 3.2. Regular addition of manure in small quantity is necessary in semi-intensive culture system, in order to ensure uninterrupted propagation of natural fish food organisms in pond.

Poultry manure or cow dung are cheaper and good source of organic manure for fish pond in rural Bangladesh. It has been observed that daily application of 8–12 kg cow dung or 5–7 kg chicken manure in one bigha pond is sufficient for maintaining optimum level of biological productivity of pond throughout the culture period. However, in some ponds, it may be necessary to add some inorganic fertilizers along with the organic manure. Addition of 0.7–1.0 kg urea and 0.35–0.5 kg TSP per bigha per week have been found good for ponds with higher density of phytoplankton feeding silver carp.

Supplementary feeding

The necessity and intensity of supplementary feeding in polyculture pond depends on the intensity of fish culture. After a certain level of fish growth, the available natural food organisms in a pond are not sufficient to support further growth of fish. In Bangladesh, the prepared balanced fish feed is expensive for rural fish farmers. Oil cakes, rice/wheat bran, other agricultural by-products and slaughter house by-products (blood, ruminant content, viscera etc.) can be used as raw materials for the preparation of home mixed feed for carps and African magur (Table VII).

Besides natural aquatic weeds in ponds, the grass carp can be fed with soft fodder grass like napier grass, and soft leaves like banana leaves. Best growth rate can be achieved, if fresh green feed is supplied at the rate of 30–50% of the estimated body weight per day. The feed should be placed on a floating frame tied to a bamboo pole. This way the feed consumption can easily be monitored. Suggested supplementary daily feeding rate can be 3–5% of estimated body weight of column and bottom feeders. Specific calculation on these species is important when the ratio of surface feeders is considerable (30–50%). Smaller food particles are also filtered by the silver carp and catla.

3.6 African Magur monoculture

Monoculture of African Magur should be undertaken only in areas where cheap, large quantities of animal protein in the form of slaughter house wastes, trash fish, fish meal etc. are available. In Bangladesh, only in the big cities like Dhaka and Chittagong a reliable, steady supply of slaughter house wastes could be collected. A number of commercial broiler farms can also supply reasonable quantity of broiler processing wastes. Fish meal is available in the cities and bigger towns, but it is expensive. There is no regular source of so called ‘trash fish’ in Bangladesh. A local commercial feed mill is producing magur feed and selling at Tk.24/kg. A few commercial magur culturist is using this feed and reportedly making profit. This feed is not yet marketed widely and, therefore, is not available to small fish farmers.

At this time, therefore, magur monoculture is feasible only in the areas where cheap, regular supply of slaughter house wastes are available.

For fish farmers intend to venture into magur monoculture, the following summarized technical information would be followed:

AFRICAN MAGUR MONOCULTURE

(In ponds without water exchange facilities)

1. Pond size : 500 – 1500 m²
2. Water depth : 1.8 – 2.00 m
3. Stocking rate : 3500 – 5000 Fingerlings (2.5 – 5.0 cm)
4. Culture period : 3 – 4 months
5. Expected production/corp : 600 – 700 kg/bigha/crop
6. Expected production/year : 8 – 12 tons/ha/year. (2–3 crop/year)

Magur feed preparation

For magur monoculture, the feed can be produced in the form of dough by mixing slaughter house wastes/fish meal/shrimp processing wastes : wheat bran/rice bran : mustard oil cake in the ratio 30:40:30. The dough may be made into balls and fed to the magur as described before under section 3.3.

Feeding instructions

The following feeding rates are recommended:

1. Fingerling (0.5 – 20 g) → 7–10% body weight/day → 3–4 times/day

2. Fattening (21 g above) → 2–5% body weight/day → 2–3 times/day

Desirable feed conversion rate : 2.3 : 1 kg (feed : magur) Price (1991) of feed : Tk. 17.50/kg

Under the present conditions, only a few sophisticated fish farm can operate magur monoculture technique in Bangladesh. The main constraint to this type of culture are:

• Lack of proper pond conditions such as inability to drain by gravitation, lack of permanent water supply facilities etc.

• Lack of proper marketing and processing facilities for handling large quantity of magur at a time.

• Lack of supply of cheap animal protein for use as feed for magur.

Storage of feed

The price of feed ingredients varies with the seasons. Therefore, it is advisable to buy large quantities when the price is low. But without proper storage the nutrient value of feed ingredients can deteriorate rapidly. Decomposed, fungal contaminated feed must not be given to the fish Relatively dry places with good ventilation, above the ground level, is a cheap and suitable place for feed storage (Fig.2). Feed ingredients should be stored in relatively dry places, above the ground, and with good ventilation. Without proper refrigeration facilities, slaughter house by-products should be used on the same day.

Regular sampling of fish:

In a proper fish production management system, sampling of fish at a regular interval is very important for:

• monitoring the growth rate of fish;

• calculating the quantity of supplementary feed required; and accordance with the increasing biomass of fish, and

• checking the health of the fish.

It is better to sample the fish (particularly magur) at every 7 days after stocking. If it is not possible to do so frequently, bi-weekly sampling must be done. In each sampling 10–20 fish of every species should be selected at random for growth measurement. For sampling, complete netting of pond by seine net is better. However, partial netting of pond also serve the purpose. Effective partial netting can be done. By attracting most of the fish to a corner by giving them some food and thus can be caught easily by netting that area of the pond. Any market size fish caught during sampling should be sold.

During each sampling, data relating to fish health and growth rate has to be properly recorded in order to keep track of the production cycle (Fish Farmers Record Keeping Format-3) growth rate, biomass, feed conversion, etc.

Harvesting of fish

Partial harvest of magur may start after 50–60 days of culture (except in carp polyculture), when some specimens reach marketable size (above 200 g).

Magur is a clever, fast moving fish. Proper nets are needed for catching magur effectively from the pond. A lot of magur usually escapes through under the bottom line of a net.

Harvesting should be done gently and quickly by seine net preferably in morning when the temperature is cooler. During harvesting, marketable fish should be sorted out first and then small size fish should be released back to pond. In polyculture or magur dominated polyculture the carp species should be sorted out first. The total operation should be done as quickly as possible so that the fishes returned to pond are not stressed.

Harvesting and marketing of fish in rural areas has to be adjusted in accordance with the market days - usually twice a week. Marketing of small quantity of fishes in batches would ensure better price in local rural markets.

Handling of fish

During partial harvesting the fish to be returned to pond must be handled carefully.

Typical mistakes made at partial harvesting in polyculture pond are listed below:

Before the start of new production cycle, total harvesting of the pond must be done. Dewatering of pond is the best way of final harvesting though it is not possible regularly in most of the local ponds. These ponds should be repeatedly netted until most of the fish is harvested and the rest should be killed by piscicide (see pond preparation).

Harvests from the pond at different dates should be recorded properly in appropriate format (Fish Farmers Record Keeping Format-4). After the final harvest, the total production can be calculated easily from a properly kept recording system (Appendix I-VII).