I spent July 15 & 16 at nearby Katmai NP during a very good salmon run. Used 80-200, 300 & 500 f4. Many used 600mm, but that seemed excessive. A 300 was optimun for many photos. Film used was Fuji Velvia 50, Sensia 100 & 400. I carried three camera bodies with a different film in each. Now I have a Fuji S2 which I didn't have then, I could have varied the ISO to suit lighting which ranged from bright sun to fog.
I believe the bears can come even closer at Brooks Falls.
At Katmai the regulations are not as strict; meaning that one can come & go when & wherever prudence dictates.