We have reached a point where the predator base is higher then the food base can support and if we do nothing it will crash. Better to kill half the seals now then lose all of them and the orcas later.
Maybe not that simple. One or two orca pods in the San Juans is not reindeer in the Pribilof Islands. They may not crash like that
http://dieoff.org/page80.htm
In Oro Bay, I see harbor seals commonly come up with all different species of fish and shellfish. No doubt they take a lot of Nisqually smolts as well.
The question is whether salmon smolts are a primary and required food source for this explosion of seals and sea lions, or whether they are just a supplement.
If a supplement, they could continue to thrive using other fish species. Harbor seals get salmon smolts seasonally, not all year long.
One of the reasons house cats are so hard on birds is that they are fed, healthy, but continue to do what comes naturally...catch birds. They don't even always eat them. One of the joys of moving from Seattle to Anderson Island, where there are few house cats, is to see birds working the ground as well as the trees.
If seals have stable food sources other than salmon, wiping out salmon won't necessarily cause a crash.
I remember a couple tens of years ago when a transient orca group entered Hood Canal. They completely wiped out the harbor seals, and salmon fishing started to be much better after that. Maybe a coincidence?
I'd be curious to know how the orca pods that focus on seals are doing. I would expect very well.
https://www.sanjuansafaris.com/whale-re ... an-channel
Maybe the resident pod will learn to eat seals. There seem to be plenty of them right now.