Well... half of these fish I'm hitting is just on exploration of new rivers. Many of the fish are not that old - most appear to be fall runs. I've never seen summers in November with tail rays and clear fins, but then again, what do I know. Of course some of the fish we are hitting are indeed summers. That being said, I highly doubt mortality is an issue with clean hook sets, quick fights and cold water. I can tell you in the last 5 years on the island, I've seen 1 dead summer run from angling. And yes you see them, they stand out like a sore thumb.
I'm not sure what to make of your comment. If you were exploring a new river, and were sighting fish that were aggressively moving to your fly, you would hit 1 or 2 after driving 2+ hours and decide to go home? I would also like to mention I go "for a few" when they are coming in, even more so than late season. Late season is just my only opportunity on the island as I don't get back out here until September.
And for the record... that last double header was taken while doing DNA sampling for DFO/MOE/BCCF. I guess I should stop at 2 fish there too and try to get the 100 fish they need over a course of 50 days?