Well, getting the eggs in is only one of the tough steps, in that it's generally a night thing. I'll save the later steps for when we get to them. There are loads of hatcheries, both stocking and commercial, down this way. NB is the east coast hotspot for aquaculture, since the company I work for is based down here and it's one of the world leaders in the industry.
As for the salmon coming back, there are divided opinions on that one. My personal opinion is yes, but there are a lot of people who claim that it's ruining the wild stocks with disease and pollutants and stuff. But like almost all issues, it's not as simple as a pure yes or no, as much as the activists like to think it is. I can point out a documentary (mockumentary?) on YouTube, if you're interested, that's extremely one-sided and full of propaganda, selective omission and loaded terminology to the point of making one sick. I'd only recommend it to someone that's not gullible and has a good ability to think critically for oneself.