Triploidization of brown trout ( Salmo trutta) by heat shocks

This study was made to optimize heat shock conditions for producing triploidy in the brown trout, Salmo trutta. Heat shock at 29°C for 10 min duration, initiated between 5 and 45 min after insemination, gave high frequencies of triploid embryos (77–91%) as assessed by chromosome observation. Shocks initiated between 90 and 260 min following insemination had no effect on polyploidization. Other groups heat shocked at 29°C for 5–15 min duration initiated 10 min after insemination resulted in moderate rates of triploidy (50–63%). A high temperature shock of 32°C for 6 min duration gave 100% triploidy but a lower temperature shock of 26°C, even for 30 min duration, had only a moderate effect (57%). Rates of hatching were generally decreased in the groups giving moderate to high frequencies of triploidy. In most treated lots haploid embryos were observed and were considered to be a cause of decreased survival.