Abstract

Induced triploidy is the only effective method currently available for mass production of reproductively sterile salmonids for aquaculture. Repeated studies at the Atlantic Salmon Federation's hatchery (St Andrews, New Brunswick, Canada) have shown only minor differences between triploids and diploids in survival to S1 smolt age (15 months), percentage of the population which became S1 smolts, and mean S1 smolt size. However, a similar study at a commercial hatchery was terminated because of exceptionally high mortality of triploids prior to the start of feeding. Marine growout trials in sea cages showed that triploids grew well in seawater, but had reduced survival rates (leading to a 5–15% reduction in yield at harvest) and high rates of jaw abnormalities. Similar results have been reported elsewhere. Although induced triploidy can be used effectively as a management tool to ensure lack of reproduction, there is at present little support of the aquaculture industry to switch to their large-scale use. In light of fundamental biological differences, it is perhaps naïve to expect triploids to perform as well as diploids using standard culture methods. Triploids should be treated as a new “species” for aquaculture development, beginning with research to determine their optimum rearing requirements.