Triploidy induction in recently fertilized Atlantic salmon ova using anaesthetics

The comparative effectiveness of five general anaesthetics as agents for inducing triploidy in recently fertilized Atlantic salmon ova is reported. Triploid rates and triploid yields following the exposures of eggs from a single female fish to nitrous oxide, and separately to Freon 22, were shown to be related to the partial pressure and duration of exposure. The maximum triploid yield (79.7%) was observed following exposure to nitrous oxide at 11 atmospheres (atm) for the first 0 min after fertilization. Triploid yields following exposure to Freon (at 1 and 3 atm) were generally lower, the highest value (43.7%) occurring after exposure at ambient pressure for the first hour after fertilization. Triploid yields in these same eggs were low ( < 10%) when halothane and ethrane were used at partial pressures in the range 0.05-0.2 atm and cyclopropane at atmospheric pressure was ineffective. In a subsequent season the eggs from ten different individual female Atlantic salmon were shown to vary little in susceptibility following exposure to nitrous oxide treatment (0-30 min after fertilization, 11 atm) and experienced high yields of triploids (mean=80.4 +/- 6.6% SD).