Pacific Northwest Winter Bottom Fishing

Hello PNW saltwater anglers, I fish the puget sound from a dock near my house. Every summer me and my brothers bottom fish off the dock using 3 way swivel rigs and frozen shrimp. In the summer this setup is a excellent saltwater multispecies rig and catches flounder, sanddab, striped perch, sculpin, dog sharks, greenling, and sculpin, but once winter comes around the bite almost completely shuts down. Recently I have tried using tiny live shrimp and have been catching really tiny fish around the docks. Has anyone else have had this problem? Any ideas about other rigs or bait to try? At this point I just want to catch a flatfish because I have not caught one in months. Thanks for any advice.