[en] We report here the first induction of gynogenesis in esocid fish by UV irradiation and heat shock. Optimal dosage of sperm UV irradiation was in the range of 1440-2160 J/m². Eggs fertilized with irradiated sperm at such dosages and not heat shocked yielded 100% abnormal larvae with the fertilization rate at 48.3 ± 8.4% (mean ± SD). There were no significant differences in survival to the eyed stage under the heat shock conditions tested (5-30 min post-fertilization for 5-30 min at 26-30^oC). Gynogens were induced in most of the groups with hatching rates at 0.2-3.3%. Optimal conditions for gynogenetic induction of muskellunge (Esox masquinongy) were the application of 30^oC for 8-10 min beginning 20 min post-fertilization, chromosome preparation, silver staining for nucleolar organizer regions, and flow cytometry measurement of the nuclear DNA content using eyed-stage embryos and larvae. Haploids hatched but died within 1 week. (author). 27 refs., 1 tab., 9 figs