I don't know what does the synopsis etc say? Crayfish are not fish - they are crustaceans and they are native and common in most waters here. In saltwater, crabs and shellfish are typically kept alive.
I don't fish for them so I have no idea. Performing a quick search
Freshwaterfish … means fin fish, shellfish and crustaceans (such as crayfish) in any life stage, including eggs.
so Crayfish and crustaceans are FISH.
It is unlawful to:
Have any live fish in your possession in the wild, or move any live fish or live aquatic invertebrates around the province or transplant them into any waters of B.C. Do not keep angled fish alive in a “livewell” or other device, or on stringers, and never use live fish as bait or release your aquarium fish to the wild.
“High-grading” is illegal.
So I would conclude it is illegal to keep them alive.
I was unable to find any similar comments either for or against keeping shellfish alive in the Tidal Fraser.