The Tidal Fraser River lacks the river current which fish can use as an advantage when you try to bring it in. In my opinion, even 12 - 15lb test is too heavy and unnecessary. My main line on the spinning reel for lure casting is always 8lb test Maxima Ultragreen. I have 10lb test on a bigger spinning reel and a baitcasting reel as I use these for bottom fishing with roe sometimes. The Shimano Sustain 2500 spooled with 8lb test was matched with a Clarus rated 8 to 12lb. This year I'm switching it to a Clarus rated 6 to 10lb, which will be a lot more fun when fighting a coho salmon.
This one last year was on the 8lb test.

This one from 2010 was on 6lb test main line, the spinning rod was 6' rated 2 to 6lb. It was an unexpected catch as the target species was bull trout. This fish decided to grab a 1/8oz spinner in 2ft of water. Again, the lack of current made it possible to land the fish with the ultralight setup.

This one was on 10lb test main line, caught by bottom fishing with roe.

Anyway, you get the idea...

Chum salmon don't bite often probably for the same reason that sockeye salmon don't bite often in the Fraser River. Water clarity is not much of an issue. These fish simply just want to move upstream. Both chum and sockeye salmon, once arrive at their natal stream, they'll bite frequently when holding in runs.
Pink salmon do the same thing to in the Tidal Fraser sometimes, they simply just want to motor upstream and will not look at your lure. This happens mostly when the tide is really low.
I have caught chum salmon by casting and retrieving spoons in the past. When it does happen, I usually catch several at once, which suggests there is a factor that triggers this sudden change in behaviour.