I've noticed that prerecorded video is on LOTS of the time. Especially in the evening once darkness has hit and -- I think -- in the "off season" much of the time, when the salmon aren't running.
Just checked it out now at 11 PM PDT, and sure enough, a 29 minute and 30 second prerecorded video is on. You can see it's a video on the bottom of the screen with the slide bar moving and the video length and status information showing. I also see right now that at the lower right of that screen it says "off air".
Not that any of this detracts from the excellence of this feed! And in daytime, especially "in season", it's a live feed more often than not.