Pacific salmon gene expression during the critical early marine period
NSERC Postdoctoral research; advised by Dr. Kristi Miller (Saunders), Dr. Scott Hinch, and Dr. Tony Farrell
Salmonids have a complex life cycle, transitioning from freshwater to marine environments and migrating long distances to feeding grounds and back to reproduce. Beyond the osmotic challenges and other stressors associated with transition between environments, salmon must grow rapidly and accrue sufficient fat to escape predation and migrate. In southern British Columbia (BC), many wild salmon populations are in decline, in part due to environmental changes associated with climate warming. Reduced survival of fish during early marine residence is associated with the declines, possibly due to enhanced environmental stressors and/or sensitivity to stress during this critical transition period. However, there is a paucity of information on salmon physiology during this critical period, including physiological changes associated with seasonal behaviours and stressors. Hatchery programs are used to supplement shrinking wild populations and augment fisheries, but hatchery-bred fish released into the wild tend to experience higher mortality than wild fish. Physiological differences between hatchery and wild fish have not been described.
Restoration of native biodiversity in altered environments
Atlantic salmon (Salmo salar) were once abundant in Lake Ontario. Reports suggest that Lake Ontario Atlantic salmon were so abundant that people could walk on their backs during spawning runs, kill them with pitchforks and clubs, and capture over one thousand fish in a night! Unfortunately, this prolific population was extirpated by 1900 because of human-mediated habitat degradation and overfishing.
The habitat in Lake Ontario and its tributaries has been largely revitalized and should now support Atlantic salmon; however, recent attempts to restore Atlantic salmon have yet to succeed in producing a self-sustaining population, suggesting that other genetic and ecological factors should be considered for restoration. Here, I will examine the performance of three source populations of Atlantic salmon that differ in the extent of genetic and ecological suitability to the current Lake Ontario environment.
Relative risks of inbreeding and outbreeding
The negative consequences associated with inbreeding depression in small populations may be similar in scope to those associated with outbreeding depression (a detrimental result that may arise from mixing populations to avoid inbreeding issues). An evaluation of the relative costs of inbreeding and outbreeding is needed for the genetic management of small populations.
This was one of few studies that have examined the risks of inbreeding and
outbreeding using wild reciprocal transplants as a tool in addressing conservation
issues in small fish populations. The study was a collaborative project
with the Department of Fisheries and Oceans (Dr. Pat
O'Reilly) and Dr. Dylan
Fraser. Other studies on the subject are usually confined to testing for
outbreeding and inbreeding depression in a common-garden environment which may be too
benign to detect fitness effects and are not an ideal representation of the native
We evaluated the anti-predator responses of juveniles from two divergent wild Atlantic salmon populations, the major farmed strain used in regional aquaculture, and their wild-farmed hybrids (F1, F2, and wild backcross). We also evaluated the competitive abilities of each cross using pair-wise aggression contests and tested whether these contests could be used to predict survival in semi-natural stream environments varying in the proportion of wild-farmed hybrids.