most these guys are partially right, fishing for fish you can't see gives you an advantage. but main reason they are not hitting your mepps, is because it resembles food. they mainly hit things that agitate them and bother them, if you look at most of lures that work for river salmon, are either fire tiger pattern or fluorescent colours or something with wide wobble(kwikfish/flatfish) even hot n tot, that doesn't look like any bait fish. i catch any salmon that sees me all day. key is to get them to snap and bite your bait. spoons and spinner more or less resemble food, and they are not there to eat. they are there to protect the redd and fend off things that might cause threat to their spawn.