The results of genetic inactivation of dace, Leuciscus leuciscus (L.), gametes using UV irradiation are presented. Dace sperm was genetically inactivated with UV irradiation doses ranging from 384 to 3840 J m-2. The most effective dose, expressed as a high percentage of hatched haploid larvae, was 1920 J m-2. The UV treatment did not kill the spermatozoa, and following irradiation the activated spermatozoa exhibited a high percentage of motility. The percentage of hatched larvae in all the experimental groups, in which genetically inactivated dace eggs were fertilized with spermatozoa from the yellow form of ide, Leuciscus idus (L.), was much lower than in the control groups. All haploid larvae showed morphological abnormalities known as "haploid syndrome" that included stunted bodies and poorly formed retinas. The optimal doses of UV irradiation ranged from 3456 to 4608 J m-2, as it was within this range that almost 100% haploid larvae were produced at a hatching rate of over 15%. Lower UV doses led to abnormal embryonic development.
