I worked at the Capilano hatchery many years ago when they had net pens in Indian arm. They kept the smolts in the pens longer than a few weeks, and the mortality was extremely high. Many got grossly distended bellies from kidney infections. It was kind of the signal to let them all go when there were lots of dead ones. Obviously some survived, as there was a fishery from the returnees near the power plant, but the initial mortality was very high, that may have been part of the reason it was discontinued, Im not sure. Atlantic salmon farmers learned early on they had to keep their smolts in fresh water longer to reduce mortality, and there are some trials being done on keeping chinook smolts in fresh water longer and feeding them less to see if the excessive hatchery mortality can be reduced. Do you see those symptoms in the Sooke pens? Forcing them into salt water directly from the hatchery seemed to cause a lot of health problems, as that's not the way coho and chinook smolts naturally acclimate, they spend time in the estuary, go in and out of the salt water, and spend time in brackish water. Pink and Chum fry head straight to the ocean soon after hatching so are probably more suitable for net pens (They are the primary species ranched in Alaska using net pens). Based on that experience I'd guess the same thing happens to many of the Sooke chinook net pen smolts, but perhaps just isn't observed?