No Dave you're jumping to a conclusion that is not supported by the evidence. Read the paper.
https://www.documentcloud.org/documents/4111834-Feist-Et-Al-Pre-Print-2017.html
We know where the problem is with the decline of coho. It's the first few months when the smolts enter the ocean. This effect is with both hatchery and wild coho. In the past our hatcheries had a smolt to adult return rate of 15% , now it is around 2%. The question that is being investigated currently is what is causing this. Fix that and our coho populations will rebound.