The work on induced breeding of carps by hypophysical injections met with full success. Large-scale production of fish seed of several cultivated species has been achieved in a number of farms, although major production was largely concentrated on the Hlawga fish farm. By this new technique, it was possible to produce spawn in excess of the present requirement and the earlier practice of collection of spawn, fry and fingerlings from rivers has come to an end.
The technique of hybridization of carps by artificial fertilization of eggs by stripping was demonstrated to the fishery workers so that they could learn the technique for future work in this line. Two hybrids were produced by reciprocal cross of the two important cultivated species, namely, catla and rohu. The growth and survival of these hybrids were quite satisfactory. The hybrids possess some characteristics which are superior to the parent species. Out of the two, catla-rohu (male catla x female rohu) was observed to have grown faster than rohu-catla (male rohu x female catla).
Loss of fish seed through heavy mortality during the three important operational stages of rearing is very common. Attempts have been made to reduce mortality especially in the nurseries so as to assure optimum production of fish seed. Care was taken at every step of nursery preparations right from the clearance of nurseries of predatory animals, liming and fertilization of ponds, collection and assessment of natural fish food, eradication of predatory insects, judicious stocking rate of fry, supplementary feeding and finally thinning and harvesting of advanced fry. By following improved techniques and proper vigilance, the survival rate could be increased 10 – 15% to at least 30 – 40% in several cases.
Although facilities for conducting experiments on intensive fish culture were limited, demonstrations arranged in two fish ponds on intensive fish culture gave very encouraging results. Stocking with a number of compatible species and following a programme of pond fertilization and regular feeding with artificial food, the production obtained was very high. One of the ponds gave a total production of 10 390 kg/ha/annum, whereas the other pond (0.12 ha) produced 4 372.5 kg/ha/nine months. The results demonstrated that by proper management, production of fish in Burma can be increased considerably by intensive culture of compatible species.
Observations made on the survival and growth of the recently introduced phytophagous Chinese grass and silver carps in Burma, have clearly demonstrated that these exotic species have already survived the critical period and have grown to adult size. The stock maintained at present at the Hlawga fish farm is quite adequate for carrying out successful induced breeding experiments by the next breeding season, when these are expected to attain full maturity. It is likely that these two exotic carps would prove to be welcome additions to the indigenous cultivated species of Burma.
Throughout his mission, the expert took special care to train as many workers as possible on various aspects of pond fish culture. It is gratifying that the training gave fruitful results as is evidenced by the successful induced breeding and large-scale production of fish seed by the trained staff. Over twenty fishery officers and field staff of the Directorate of Fisheries and PPFB have received training in scientific pisciculture and especially in the technique of breeding carps by neuro-hormonal treatment.
