My master's research focused on the evolutionary ecology of sea lice, farmed and wild salmon. I'm particularly interested in the ways in which the combination of wild salmon migrations and salmon farm management can influence chemical resistance evolution on farms.

Sea lice tend to proliferate on sea-cage farmed salmon, resulting in economic costs to the farmers. These outbreaks can also affect wild populations, which raises concerns about population conservation and the environmental costs of sea-cage aquaculture. Salmon farmers address these concerns with integrated pest management (IPM) strategies that include chemical treatments. These chemicals can reduce parasite numbers, but over time, parasites can develop a resistance to the chemicals.

In coastal B.C. new conservation regimes rely on increased use of chemical treatments, which is classically associated with resistance emergence. Achieving conservation goals could then actually increase the risk of resistance emergence; however, flow of susceptible genes from lice on wild fish into populations on farms could delay resistance emergence (similar to "refuge" planting in agriculture).

Wild salmon demography

Sustained exchange of parasites between wild and farmed salmon, combined with wild salmon migrations can alter dynamical patterns in salmon populations. Notably, patterns of line dominance in pink salmon may change in the presence of farms. Line dominance can either increase or decrease, depending on the way in which salmon farms respond to infections.

In a follow-up study, coworkers and I show that sustained spill-back into wild reservoir hosts can result in an Allee effect in the wild hosts.

Parasite evolution

Goal: Understand feedbacks between increasing chemical use, conservation and resistance management in the context of sea lice, wild salmon and salmon farms.

Hypothesis: Wild salmon serve as evolutionary refuges, slowing resistance evolution in sea lice.

Questions:

  How do wild salmon migrations near farms affect time to resistance emergence?

  • Specifically, how do management actions (treatment, stocking density) affect time to resistance?
  • What are the effects of biological assumptions?

  How does varying synchrony of treatments on groups of farms change things?