Juro, I agree with much of what you say. The use of hatcheries is quite a hot topic over here, as we look for ways to reverse the decline in salmon numbers. For my part, I doubt their value in many situations. Too often they are a relatively easy 'solution' to declining runs, which avoids addressing the real underlying problems. Many of our rivers are quite acidic and support little invertebrate life; there is thus a finite number of parr that they can support, and the population will always regulate itself down to this level. Stocking a river that already holds its quota of parr will not add a single adult fish to the returning runs, and a relatively small number of successful redds can fill a river to capacity. As with pacific salmon, nature produces a huge surplus - I believe that the average annual run of salmon in the Spey equates to the output of about 10 successful spawning pairs (assuming zero mortality, of course!).
Having said that, we have a few rivers (eg the Wye) where the runs have fallen so low that the river may no longer be stocked to capacity with parr. In these circumstances a hatchery does have benefits. They can also help increase a run of salmon by stocking tributaries that are inaccessible to spawning fish (eg where there is an impassable obstacle). But they should not be regarded as a substitute for habitat improvement. I also firmly believe that it is desirable to stock with offspring of fish from that same river, which will have adapted over millennia to suit that particular water and are to some degree genetically distinct. If native brood stock are not available, it makes sense to try to match the river conditions as closely as possible.
You say the Greenland fishery is the biggest threat to salmon, and I would not wish to underestimate its impact. However, there is quite a well-founded theory that global warming may be a significant cause of the decline we have seen recently. Evidently the area of the atlantic which is the right temperature for salmon to feed has shrunk dramatically with the melting of the polar ice cap. My knowledge is fairly sketchy, but it has been suggested out that, along with the by-catch of post-smolts by Russian mackerel trawlers, this is the only factor that has changed in recent years, coinciding with a serious decline in runs of salmon (particularly 2+ sea winter fish). This is a much more serious problem than netting, and one that cannot be cured with mere money. I believe it was raised at last summer's international salmon symposium in Edinburgh; unfortunately the papers haven't been published yet.