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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
August 2017
ABSTRACT:
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.