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EFFECTS OF DIETARY THIAMINASE ON REPRODUCTION IN THREE STRAINS OF ATLANTIC SALMON
2 Department of Biology, Western University
1151 Richmond St., London, Ontario, N6A 5B7
The reintroduction of Atlantic salmon into Lake Ontario is a top priority for management agencies and conservation groups. However, these reintroduction efforts have not yet produced a self-sustaining population of Atlantic salmon. One major factor that has been hypothesized to obstruct reintroduction efforts is the high abundance of exotic prey fishes—rainbow smelt and alewife—in Lake Ontario. Unlike historical prey, these introduced species contain high levels of the enzyme thiaminase, and their consumption has been associated with a thiamine deficiency in a variety of Great Lakes salmonids. Working on Atlantic salmon, my lab has previously identified negative effects of dietary thiaminase on traits that include swimming performance and body condition. Importantly, these effects differed among the three Atlantic salmon strains targeted for reintroduction into Lake Ontario, suggesting that strain selection could help mitigate these negative effects. However, some of the most serious effects of thiamine deficiency are predicted to occur during the reproductive phase, but these effects have never been compared among strains. In this project we quantified the effects of dietary thiaminase on reproductive traits in Atlantic salmon and compared this effect among the three candidate strains. We found that the high-thiaminase diet did not affect sperm motility or sperm velocity. We found no difference in offspring survival between males fed a high-thiaminase diet and males fed a low-thiaminase (control) diet. However, offspring mortality prior to the onset of feeding was higher when females were fed a high-thiaminase diet than when they were fed a low-thiaminase diet. The effects of dietary thiaminase on reproductive traits did not differ significantly among the three populations of Atlantic salmon. Overall, the high-thiaminase maternal diet was associated with about a 60% increase in egg morality relative to the low-thiaminase maternal diets, which suggests that dietary thiaminase may be an obstacle to the re-establishment of Atlantic salmon in Lake Ontario. The comparable performance of different populations on the high-thiaminase diet suggests that strain selection is unlikely to provide a clear solution to this potential challenge.