Those fish don't have to pass any feedlots on the way out to the ocean, do they?
You must know Washington State raises Atlantic salmon in net pens. What may not be known is what Columbia River sockeye juvenile migrants, and specifically the stocks mentioned, do when meeting the Pacific. They have 3 choices … head south to probably warmer water, not a wise choice according to recent science; head due west to the open ocean; or head north to mingle with Fraser, Skeena, Nass, Alaskan, and Russian stocks in the N. Pacific and Bering Sea. I don't pretend to know how they migrate or where they go but I would bet it's where other sockeye stocks mentioned above rear successfully.
If that is indeed the case these stocks probably migrate past the same BC salmon farms Fraser stocks do.
Too bad there isn't more data on this but that's coming from David Welch and a host of big name scientists (sorry, Alexandra Morton was not asked to collaborate). Big bucks have been promised to track seaward bound salmonids, including fish on routes past active salmon farms.
Would love to dig up the link for you but it's Saturday night … look on the Cohen site for the proposal and details.
Or google P.O.S.T.. Dr. David Welch