Effects of Two Activated Milt Residence Times on Landlocked Fall Chinook Salmon Egg Survival to the Eyed Stage of Development

During salmonid spawning, the amount of time required for activated milt to successfully fertilize eggs has not been well defined. This study examined the effects of two different activated milt residence times, 20 and 60 s, during production-scale artificial spawning of 20 landlocked fall Chinook Salmon Oncorhynchus tshawytscha. Mean (SE) survival to the eyed stage of egg development was 29.2% (5.5) in the eggs that were subjected to the 20-s milt residence time, which was not significantly different from the 32.3% (5.7) survival rate for eggs with the 60-s residence time. There was considerable variation in egg survival among the individual female spawns, ranging from near 0% to 76.7%. These production-scale results indicate that activated milt residence times as low as 20 s can be used during the landlocked fall Chinook Salmon spawning, with no significant effect on egg survival to the eyed stage of development.