Most of the local rivers have sturgeon populations at the mouths. I've heard of them in the Stilly and Snohomish for 20 years now.

So... if they are at those river mouths, then why wouldn't they be ganging up in front of the locks?

My guess would be a bunch of green sturgeon in the lake that went thru the locks.

Greens are the ones that usually live around river mouths.

One of the old Stan Jones freshwater fishing books had a picture of a guy holding a green. I think the Duwamish was mentioned.