How much do I tip?
How hard does the guide work? That gives me the answer.
Did the guide hold the boat against the current so I could make repeated casts to a good fish? Was the guide polite and helpful? Did I learn from the guide? Did the guide know his (or her) stuff?
It is not up to the guide to make the fish bite. It is not up to the guide to make the fish stay on the hook. It is up to the guide to give me a shot at the fish. If the guide is competent, honorable, and hard-working, I try to tip well. Some jobs have the assumption of tipping built into their pay scale. I think that guiding is one of those things. It provides the customer with a chance to make a very telling comment on the service received.
Ed