When discussing gillnet fisheries, it's important to distinguish between impacts on salmon and steelhead, because the two are quite different, in terms of both who conducts the fisheries and the overall impact those fisheries create.

Adding on to what Carcassman said, the only gillnet fisheries our government can outlaw are the non-tribal ones, and they fish for strictly salmon. I could easily stand to see those go away, but it would represent very little reduction in gillnet harvest overall (except in Willapa Bay, where I think all your concerns are valid). As Carcassman said, the vast majority of salmon are harvested in open ocean, mixed stock, hook and line fisheries (both commercial and recreational).

As regards steelhead, the decision to stop gillnetting them lies solely with each of the treaty tribes, so an audience at UW might not be the most effective forum for that discussion. I do believe, considering that there are no non-tribal, commercial fisheries targeting steelhead, yet the numbers continue to decline, even in places where habitat has been well-preserved or enhanced, that tribal gillnet fisheries have played and continue to play a larger role in limiting steelhead abundance versus salmon. I'm probably wrong. As you're no doubt learning as you research this topic, it's extremely complicated, and clear answers are hard to come by.

Good luck!