Whidbey FF, the activity in the salt definitely drops off during the winter months for the North Sound area, excluding the west side of the Sound.
Unlike the South Sound, and salt water on the West side of the Sound, the cutthroat here migrate upstream and tend to stay there until Spring, so the fishery tends to shift over to fishing the larger rivers and tribs. for salmon, steelhead, bull and cutthroat. Of course, a Whidbey Island fisherman with patience and persistence can target the Winter Steelhead headed for those rivers as they migrate past South Whidbey Island areas.
This area does not have the large juvenile Coho fishery or coho hatcheries found in the south Sound, although an occasional resident Coho can still be found off of the North Sound beaches during the winter, as well as isolated instances of picking up some smaller searun cutthroat, both of which I've done when faced with cabin fever and a break in the weather that sends me out to practice casting from the beach. South sound is geologically unique from this area, and that entire area is more akin to an estuary, where fish can easily winter over close to their spawning streams. Anyway, that's my two cents worth.