Rifleman, I think we're basically in agreement. It isn't an either/or proposition, but I'd come down on the side of "carrying a shotgun is excessive" whether hiking or canoeing, except
under the circumstance you and I both mentioned, i.e. traveling in very-large-bear country. And even then, it would depend -- if you're in a group of 4 or more and practicing routine "bear hygiene," you're unlikely to be bothered by brown bears in actual wilderness, where they're not acclimated to humans. On the other hand, a friend (no longer with us, alas) who was addicted to solo canoe travel in the far north never went without her Winchester Defender, and, yes, Brenneke slugs (totally with ya on those). And I'd never travel in polar bear country without one.
But carrying a shotgun on a local dayhike, outside of hunting season, would feel a bit... ostentatious... to me. And I'm not gonna lug the weight of something that's no fun to plink with!
... the idea of camping/trekking by canoe/kayak sounds very appealing.
There's nothing finer... you can travel hundreds of miles in 2-3 weeks if you want (we like to go slower than that), and at least in a canoe, take gourmet food and pretty much whatever creature comforts you desire. And it's a lot easier on older bones, especially if you have a young relative along to carry the heavy stuff on the portages.