Quazi Zahangir Hossain*
Environmental Science Discipline, Khulna University, Khulna 9208, Bangladesh
Sk. Mustafizur Rahman
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna 9208, Bangladesh
Breeding behaviour, Induced breeding, Larval rearing, Ilish bata, Labeo bata
Jhenaidah district
Animal Health and Management
Brood collection: Fourty female (117-150 g in weight, 131 g on average) and 60 male (96-140 g in weight, 114 g on average) broods were collected from the natural source of Jhenaidah district in July, 2003. Collected broods were transported to the Government Fish Seed Multiplication Farm, Khulna Sadar, Khulna in well aerated tanks.
Breeding behaviour: The breeding behaviour was observed in hapa (280 x 160 x 45 cm), which was separated in four chambers by clothing that formed a raceway. The hapa was placed in a concrete cistern (300 x 180 x 75 cm) where 30 cm water depth was maintained with circulating water at rate of 200 ml-sec. A continuous observation in daylight was done from the above and the sides of the cisterns to record the breeding behaviour. Male and female breeders were kept separate until the second dose to the females. After second injection to the females, both female and male breeders were transferred to breeding hapa providing water flow and showering. Recording of behavioural observations was started as males showed increased activity and 'interest' to the females’ immediately after transfer to female hapa. Recording of behaviour was started as soon as there was a noticeable increase in courtship activity for up to 90 min by which time of breeding activities usually ceased.
Induced breeding: Five trial doses to the females were administered to optimize the dose of PG. The females were first injected intraperitoneally at the rate of 0.5, 1.0, 1.5, 2.0 and 2.5 mg PG-kg body weight and the second injection at the rate of 3.0, 4.0, 5.0, 6.0 and 7.0 mg PG-kg body weight. Dose interval between the first and the second injection was 6 hrs. At the time of first dose to females, male fishes were administered single constant dose of 1.5 mg PG-kg body weight. Each experiment was conducted with three replications and each replication was consisted of three males and two females (3:2). The breeders were removed from the hapa when the natural breeding completed. Water hardened eggs were transferred to the incubation jar. To determine the rate of fertilization, three samples of eggs were observed under compound microscope after 3 hrs of ovulation. Transparent eggs with cell divisions were considered as fertilized; on the other hand translucent eggs with milky colour were regarded as unfertilized. Three samples were taken to record the hatching rate. One hundred (100) eggs were put in a small floating plastic cylinder (dia.10 cm) with a nylon mesh at the bottom and placed in conical bottom incubation (cement) jar. The hatchery water quality was maintained within suitable range for the breeding activity.
Larval rearing: After eradication of backswimmers by dragged chatjal (net made of coarse cloth), raw cow dung (500 g) with Urea (50 g), TSP (30 g) and MP (10 g) spread as manure in each nursery pond of 0.004 ha. The pond was also manured by mustard oil cake (200 g) for the next day followed by cow dung application. The spawn released in the nursery pond after fourth day of first manuring.
After stocking the spawn, pond water increased to a minimum level (about 2 cm) for each day of nursing and mustard oil cake (250 g-day) as food was applied except the day of netting. After one week, chatjal was dragged for stretching the spawn. After two weeks of nursing all fries were transferred to the rearing pond. Some physical and chemical variables of the nursery ponds water were recorded daily and weekly intervals respectively at noon. Water temperature and secchi disc reading were recorded daily at noon. The pH, total alkalinity and total hardness were measured at weekly intervals.
Khulna University Studies, Special Issue (1st Research Cell Conference): 141-147, 2006
Journal