The major part of the experiment was conducted at the Laboratory, Department of Fisheries and Marine Bioscience, Jessore University of Science and Technology (JUST), Bangladesh. The experiment was done from 10 March to 30 June 2014. 2.1 Brood fish collection and rearing Samples of M. pancalus for induced breeding were collected from Jhapa boar, Jessore and were kept in the previously prepared experimental pond of the university. For successful induce breeding, proper rearing and maintenance of brood stock is a pre-requisite. Monthly manuring and fertilization was done with cow dung, urea and TSP at 5 kg/decimal, 250 g/decimal and 100 g/decimal respectively to stimulate the growth of natural feed. Liming was also performed whenever necessary at 250 g/decimal. Besides this, the fishes were fed daily with a mixture of mustard oil cake, rice bran, wheat bran, and vitamin premix at the ratio of 20:49:30:1 by weight at 5% of total body weight of fish.
2.2 Brood fish selection The ripe and healthy male and female brood fish were selected based on physical and visual examination of secondary sexual characteristics i.e., size, color, swollen abdomen and genital openings. Males were comparatively small in size, developed with dark greenish color on the top and whitish in beneath. While mature females were comparatively large in size, greenish color on the top and yellowish in beneath with soft and swollen abdomen. Mature males and females from the brood rearing ponds were collected and kept in the laboratory aquarium.
2.2 Brood fish selection The ripe and healthy male and female brood fish were selected based on physical and visual examination of secondary sexual characteristics i.e., size, color, swollen abdomen and genital openings. Males were comparatively small in size, developed with dark greenish color on the top and whitish in beneath. While mature females were comparatively large in size, greenish color on the top and yellowish in beneath with soft and swollen abdomen. Mature males and females from the brood rearing ponds were collected and kept in the laboratory aquarium.
2.5 Measurement of water quality The water quality of the experimented aquarium were maintained and recorded carefully. Water parameters such as dissolved oxygen (DO), pH and water temperature were measure daily. A pH meter (EZoDO; Model-7200; Made in Taiwan) was used for the measurement of pH and temperature; a DO meter (LTLutron; Model- YK-22 DO; Made in Taiwan) was used for the measurement of DO.
2.6 Hormone administration The hormones were administrated near the base of pectoral and dorsal fin at an angle of 45° with the body. Then the fishes were caught very carefully from the spawning tank and a piece of clean, soft and wet cloth was used to wrap up the fish. The amount of hormone for each fish was determined before according to the body weight of the broods. After the administration of hormones the fishes were kept in separate aquarium which supported a continuous air flow and at the sex ratio of 1:1 for breeding.
2.7 Determination of fertilization and hatching rate The eggs were examined to determine the fertilization rate. The M. pancalus laid their sticky eggs on the root of water hyacinths. Approximately 60 eggs with roots were placed in plastic bowls with three replications of each having water flow from porous PVC pipe and outlet facility. The fertilized eggs were transparent and unfertilized one became whitish. The eggs were observed under a magnifying glass and fertilized eggs were counted with the help of a soft thin brush.
2.8 Statistical analysis The results found in the study were subjected to statistical analysis, chi-square test that showed the significance (P<0.05) level of differences between the treatments. This statistical analysis was performed with the aid of the Microsoft Excel 2010.