I think sight/movement has more to do with catching fish than scent. Ive caught steelhead with 4 day old whitish/black stanky sandshrimp, and jigs that were rolled on by a dog. A buddy of mine smokes like a chimney and has no problem hooking up.

Im not saying that scent plays no factor, but it is over-emphasized big time... my 2 cents
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"I have a fair idea of what to expect from the river, and usually, because I fish it that way, the river gives me approximately what I expect of it. But sooner or later something always comes up to change the set of my ways..."
- Roderick Haig-Brown