2. MATERIALS AND METHODS

2.1 Fish Culture Sub-System

Pond selection for culture demonstration

Of the 7 ponds selected for demonstration of magur grow-out culture techniques 5 were in the facilities of Fish Seed Multiplication Farms (FSMF) under the Department of Fisheries (DoF) and 2 were in the private farms (Table I)

TABLE I: DETAILS OF CULTURE/DEMONSTRATION PONDS USED IN THE PRESENT STUDY

Culture techniques

Considering the available facilities and inputs, the following three culture techniques were demonstrated in the 7 selected farm ponds (Table I).

1. Magur dominated polyculture

In this system, African magur was cultured along with surface feeding carps (Hypophthalmichthys molitrix and Catla catla). In Faridpur FTEC pond along with surface feeders some bottom feeders like Mrigal (Cirrhinus mrigala) and Mirror carp (Cyprinus carpio var. specularis) were also stocked. African magur constituted the major portion (62% – 85%) of the stocked fish. Supplementary feed was regularly supplied to magur in adequate quantity (detailed under feed preparations, feeding rate and feeding method).

2. Magur dominated polyculture integrated with chicken

Stocking rate and ratio of fish were almost similar to that of magur dominated polyculture system but the only additional thing in this system was that the pond fish culture was integrated with chicken rearing. Thus the fish was continuously fed by the chicken (housed above the pond water) in the form of excreta and waste feed. In addition, supplementary feed was given in small quantity for magur. The chicken house was built on the pond water surface making provisions for the chicken excreta and waste feed to drop directly in the water below the floor of the chicken-house. This arrangement allowed the magur to feed on the chicken excreta and waste feed as they dropped in the water.

3. Magur monoculture

Under this system only African magur was cultured in ponds. Supplementary feed was given to magur in adequate quantity on a regular basis.

Pond preparation

Usual pond preparation techniques i.e. dewatering, liming, manuring and fertilization were followed. Except in pond-7, all of the ponds were completely dewatered and sun dried. As pond no.7 could not be dewatered, rotenone was applied at @3 ppm in order to eradicate predators and unwanted fishes. After 3–4 days of dewatering (or rotenone application), the ponds were treated with lime at @140–735 kg/ha in dried ponds and at @1135 kg/ha in the pond with water (pond no.7). Manure in the form of dry chicken excreta was applied at @2.5–3.5 t/ha. The dewatered ponds were filled in with water either from the neighboring ponds or from deep tube-wells. A few days later, when the plankton bloom appeared, the ponds were stocked with fingerlings.

Stocking

Stocking rates and ratio varied from pond to pond. Stocking details are presented in Table II.

In magur dominated polyculture system, stocking rate varied from 10,150 – 20,729/ha of which African magur constituted 62%–85% (8,600–12,800/ha) while 15%–38% (1550–7885/ha) were carps.

In magur-chicken integrated polyculture system, stocking rate varied from 15,265–34,100/ha of which African magur constituted 76%–96% (12,000–32,790/ha) while 4%–24% (1,310–3,856/ha) were carps.

In magur monoculture system, stocking rate varied from 20,000– 45,400/ha.

Size of fingerlings at stocking varied from pond to pond. Average weight of magur fry fingerlings at stocking ranged from 0.4 g – 8.5 g while for carps it varied from 7–200 g.

Fingerlings of magur and carps were supplied from different DoF Fish Seed Multiplication Farms (FSMFs).

Water management

No attempt was made to change water or replenish any evaporation or seepage loss of water in any pond except pond no.3. at Tongi, FSMF in which periodic replenishment of water was made. The water levels in the ponds during the culture period, were 1.5 to 2.1 m. Because of artificial feeding, the organic loads in the water were high. However, the fish did not show any sign of distress.

TABLE-II: STOCKING DETAILS OF CULTURE/DEMONSTRATION PONDS

Culture period and size of fish at harvest

Initially, magur was harvested when they attained a size of over 500 g. However, later on, magur was harvested when they attained the size range of 200–450 g depending on market preference. Culture period varied from 60–115 days. Because of the short duration of the magur culture period, most of the supplementary carp species did not reach market size. The carp species were used in the next magur dominated polyculture that followed immediately in the same pond.

Feed ingredients

It is well-known that most of the production cost come from feed. The ratio of feed cost compared to the total cost increases proportionally with the intensity of production. The success of magur culture mostly depends on the quality and quantity of artificial feed and on the intensity of feeding (Vivien et al. 1986). Even though the species is carnivorous by nature, less cannibalism occur if the fish is fed adequately.

Only locally available ingredients were used in preparing the feed for magur. The slaughter house wastes such as blood and viscera were used as a source of animal protein. Where ever it was possible, attempts were made to collect and incorporate these in the feed of African magur.

Most of the farms organized regular collections of slaughter house wastes. During shortage of slaughter house by-products the magur feed was supplemented with locally available fish meal. At jessore FSMF, African magur was fed with trash fish. BIMAN Poultry Complex used chicken viscera, chicken blood and feed mill waste which came from their own slaughter house and feed mill.

Other ingredients used were agricultural by-products e.g. Rice bran, Wheat bran, Mustard Oil Cake, etc. Depending on local availability, different diets for magur were prepared and used (Table III).

TABLE - III: FEED INGREDIENTS: QUANTITY AND PERCENTAGE COMPOSITION

Feed preparation, Feeding rate and Feeding method

The daily feed ration was fixed according to the estimated biomass of magur in the pond. Biomass of other species viz. Silver carp, Catla, Mrigal etc. was not considered in feed calculation. However, it was estimated that about 10–15% of magur feed was consumed by the carps. In most places, the quantity of feed was corrected after each sampling. Depending on the size, the daily rate of feeding varied from 5–30% of the body weight of magur. Because of the use of fresh (or frozen) animal blood and viscera the diet had a considerable amount of water content. The feed was prepared daily. The viscera, when used, was chopped or minced before mixing with other ingredients. The mixed dough was shaped into ball or pie and was fed to the fish in certain fixed locations of the pond.

In magur dominated polyculture (pond no. 1 & 2), magur monoculture (pond no.6 & 7) and one trail of magur integrated with chicken (pond no.3 at Tongi, FSMF) supplementary feed was given as per the following schedule:

In magur-chicken integrated system, supplementary feed, was given from the 10th days. The feeding rate was gradually reduced from 30% of body weight to 5% of body weight by the average size of 100 g, and then onward until harvest, the daily ration was maintained at 5% of the body weight, as shown below:

The fish were fed twice a day. First feeding was done in the morning at 8–9 o'clock and second feeding at 4–5 PM in two equal portions. In the beginning of the culture period feeding trays were used to check the consumption. After some days, when the fish had learnt where the feeding place was, feed balls were directly dropped into the pond water. It was always given in the same place.

Sampling, Harvesting and Marketing

Originally it was planned to sample each pond at 10-day intervals. In reality, however, these samplings were made at different time intervals. Seine net was used to catch the fish. At random 20 magur and 10 fishes of other carp species were measured. At the same time the health condition of the fish was checked. At final harvesting the whole pond was dewatered. All fish in the pond were weighed and the total number of fish harvested were recorded. Trial sales of harvested fish were carried out at local markets to ascertain the price and customer preference in relation to fish size.

2.2 Chicken Sub-System

Chicken varieties

Under the chicken sub-system, three different varieties of chicken were integrated with fish culture. Layer chicken Phoymee and Hisex Lohman hybrid were used at Natore FSMF and Gachihata A.F. Ltd. respectively. In Tongi FSMF, hybrid broiler chicken (White rock female × Cornish male) were reared. Details of chicken used in the integrated culture are presented in Table IV.

TABLE IV: DETAILS OF CHICKEN USED IN THE INTEGRATED CULTURE SYSTEMS

Nursing of day-old chicks

The day-old broiler chicks were kept in a separate circular brooding confinement which is made up of bamboo split. The diameter and height of the confinement was 1.8 m and 0.5 m respectively. The floor of the confinement was covered with news paper for first 1–2 days and then rice husk was placed. The temperature and light requirements of chicks were maintained with the provision of electric light. After 12–14 days of nursing the chicks were shifted to the house on the pond.

Chicken house

Chicken houses were constructed above the pond water. The floor and walls of the houses were made up of bamboo materials and the roof was made up of tin sheets. The size of the house was calculated at at the rate of 0.23 m² for a layer chicken and 0.12 m² for a broiler chicken. Chicken were always kept confined in the house throughout the culture period.

Chicken feed

Both the broiler and layer chickens were regularly fed with recommended prepared feed.

The layer chicken were feed twice a day i.e. between 8–9 a.m. and 4–5 p.m. and the broiler was fed thrice a day i.e. morning (8–9 a.m.), noon (12–1 p.m.) and afternoon (4–5 p.m.). Clean water was always kept in self drinker in the chicken house.

Feed ingredients were purchased from the local market and the feed was prepared mixed in each farm. Details of feed ingredients and their proportions used are presented in Table V.

TABLE V: FEED INGREDIENTS AND THEIR PROPORTIONS IN FEED FOR LAYER AND BROILER CHICKEN

Diseases prevention

Both layer and broiler chickens were properly vaccinated. No disease problem was encountered during the rearing period.