I think there are two ways to respond.
In terms of doing a seal diet study, in principle it wouldn't take that long. In a couple of years you could have some information. The issue at hand, though, might be how many seal stomachs you would have to examine before you were able to meaningfully estimate the mortality that they're inflicting on salmon. If you picked the right seals, you might find that relatively few were consuming quite a lot, but you don't know that beforehand.
All that is to say that if seal predation were quite a substantive issue and they were eating lots of salmon smolts, then I think any typical diet study with seals, which would take a couple of years, might be able to detect that, but it might also be more important in some rivers than others. I would encourage the committee to think very carefully but strategically when making recommendations as to whether you're thinking about salmon throughout its entire range in Canada or whether it might make more sense to focus and prioritize on some key troubling rivers or areas.