Common ground? Let's start here.... habitat AND harvest are both important to the fish. Provide them some sanctuary to spawn/rear AND quit fishing them so damned hard. You guys want to turn this into a Miller Light commercial...
"Less filling"
"Tastes great"
JFC! It's not just one or the other.... BOTH of those critical H's must be addressed in any river system that you all want to argue about.
The other two oft-cited H's really are just smaller parts of those two bigger H's that determne whether or not we have healthy fish populations. (Hatcheries are really all about feeding the insatiable need to HARVEST HARVEST HARVEST. Hydro-electric dams are nothing more than another assault on the HABITAT)
Nobody can argue that the most important thing these critters need to maintain thriving populations is free-flowing access between a nutrient-rich ocean pasture and intact river systems with productive spawning and rearing HABITAT! You simply can't have salmon without rivers. Trash the infrastructure of the natural fish factory, and production will assuredly go down the $hitter. Without good habitat to support natural propagation of the fish, runs will remain in a state of perpetual depletion.
However, nobody can deny that harvest abuses are also a HUGE part of the problem. You can't maintain fish populations if all of your breeding stock ends up in fish totes! All the habitat in the world is worthless if we don't allow enough fish upriver to seed it!
Nobody can argue that historically we (comm and sport) have taken too many fish. The biggest argument among the users is who gets to do the killing and where the killing occurs. And when we perceive that we are not being allowed our "fair share" of the kill, we are quick to demonize the other user group(s) that are taking more than their fair share. We spend an inordinate amount of energy and $$$ lobbying for who gets to do the killing. And with each of the stakeholders asserting its right to maximize its take, enabled by a harvest-at-all-cost fish bureacracy, we end up overharvesting.... again, again, and again.
The great news is that salmon populations are incredibly resilient, and depletion from harvest abuses can be relatively quickly reversed... but only if the habitat for rebound production is still intact.
The same cannot be said for habitat abuses. Restoration/reclamation of degraded/lost habitat is a MUCH harder thing to reverse, both in terms of money and time... and given the demands of our hyperconsumptive, gotta-have-it-now society it has become nearly impossible to do so. It's much wiser and cheaper to protect, conserve, and maintain existing habitat in the first place. But as history has shown, society lacks the foresight, will, and discipline to do so.
Looking at it from the broader context of where we as a society ought to be inversting our time, talent, and treasure....
It seems we invest way too much in the arena of allocative battles over who gets to kill the last fish. If even a small portion of those resources could be re-directed toward habitat protection/restoration, we would be far better off over the long run.