Measurement and potential applications of induced triploidy in Pacific salmon

Abstract

Sterile triploids potentially could be useful in salmon culture because of the management options available with a sterile population and the ease with which triploidy can be induced. Heat shock applied for 10 min in a temperature range of 28–30° C and initiated 10 min following fertilization of eggs induced triploidy in coho ( Oncorhynchus kisutch), chinook ( O. tshawytscha), and pink ( O. gorbuscha) salmon, and in reciprocal hybrids between chinook and pink salmon as assessed by flow cytometric ploidy analyses. Moderate to high frequencies of triploid embryos were observed in all treated lots ranging from 58% (pink salmon) to 84% (one family lot of coho salmon). A substantial reduction in the frequency of triploid individuals between the eyed egg stage and 17 months was observed in one of two family lots of coho salmon. Significantly greater mean weight was observed at 17 months for diploid coho salmon (16.6 g) when compared to their triploid siblings (14.5 g). Mortality related to heat shock was observed primarily in coho salmon. Three triploid individuals were observed among 20 untreated pink salmon suggesting that triploid pink salmon may not be rare in natural populations.