Yes, we have done those analyses, and in epidemiology we'd call it a matched case-control study, where you have two sets of populations that are experiencing the same environmental conditions. One subset experiences the infestation, the other does not, and you look to see if there is a change in their productivity.
In an analysis, we've applied that kind of structure to pink salmon populations on the central coast of British Columbia, looking at changes in productivity of these populations, before and during the sea lice infestations, in relation to an unexposed area just to the north of there. The structure of the analysis allows us to control for other compounding factors that are environmental and affect the populations as a whole---so that would be large-scale climatic fluctuations. The model we used is a non-linear stochastic model, which allows us to control for environmental noise as well as density-dependent mortality.
With this analysis, we're able to isolate the effect of the sea lice infestations on the productivity of those populations. We've done that for pink salmon in the Broughton Archipelago. I'm part of a group that has now finished a similar analysis for coho salmon in this area. We're beginning to put together analysis of chum salmon in the Broughton Archipelago.
We're also starting to assemble the data to look at the relationship between sockeye salmon productivity in the Fraser in relation to aquaculture production, but we're only in the early stages of assembling the data for that.