On one trip south i put a freezer in the back of the pickup powered by a honda generator. I ran the genny a couple of hours a day to keep the freezer cold. I was not asked at the Canadian border about fish and reentering the US was the same - no questions about fish on board.
I have not seen any regulations in Canadian law or US law that limits fish transportation.
In over 10 round trips from AK to the L48 and back, i have never been asked about frozen fish in the vehicle. Firearms, alcohol, tobacco and some food items - yes, but never fish.
If there are regs that limit fish importation and transportation, please post a link - i'd like to know myself!
Good luck with your fishing trip - i've read the sockeye should be bigger this year… last year was weird...