GENETIC CONSEQUENCES OF THE SIMULTANEOUS OR SEQUENTIAL ADDITION OF SEMEN FROM MULTIPLE MALES DURING HATCHERY SPAWNING OF CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA)

Biochemical genetic variation was used to determine the proportions of progeny sired by, individual male chinook salmon (Oncorhynchus tshawytscha) in crosses derived from multiple male parents. For crosses conducted with mixtures of semen, an equal volume of semen from each of three males was pooled and used to fertilize the eggs of an individual female immediately after pooling, and after holding the pooled semen for 15 and 60 min before use. Male potency varied in these crosses, with individual males siring between 5 and 88% of the progeny of a cross. Potency differences among males were reduced with the use of pooled semen that had been held for 60 min prior to fertilization. For crosses derived from the sequential addition of semen, semen from three males was added at 45-s intervals to the eggs of a single female. In these crosses, individual males sired between 0 and 94% of the progeny of a single cross. The position occupied by a male in the fertilization sequence was a significant factor in determining the proportion of progeny that he sired, but differences in male potency were also observed.