Actually, I do see your point in that we are already at a point where we justify making "adjustments" to deal with our current sad state of affairs. Simple math would make it seem like the right thing to do, subtract b to prevent reduction of a. However still two wrongs don't make things right for the salmon and the solution to the core problem is not correlative genocide of another inter-related species thrown out of balance by our very own actions.
Case in point - sitka spruce and the pine weevil. In nature, when sitka spruce occurs in a certain density an explosion of a weevil population occurs and the trees die. This is by design in nature, and when we plant the same trees too close to each other we find out 20-30 years later that we messed up. Nature has a level of complexity that we can barely comprehend never mind master. These are just trees we are talking about, not the magnificent salmon and steelhead trout of the world.
I would respectfully contend that such adjustments aimed at erradicating other species are only band-aids that prove our ineptitude in managing mother nature correctly. In my opinion, it is a step directly in the wrong direction.
In many things, including casting instruction, we are taught to identify the core problem and treat that first and foremost. The core problem with salmon depletion is not the loon. Loss of habitat has made returns of many millions of salmonids become extinct in North America. Open seas exploitation by commercial fishermen in Greenland has been among the most impactive forces working against salmon whose home rivers range over several countries.
In nature, the birds and pinipeds serve a role in the same rhythm that all other organisms abide by, that is all but one. In my most humble opinion, the best thing we can do is to ensure that nature is given enough berth to achieve her magic and play God the very least possible, or better yet not at all.
Thanks for the compliments on my casting