I worked on a charter fishing boat for a while in college. I sold myself on the "I get to fish every day" dream. Very little actual fishing, lots of hard work and long days. Not everyone is a dream fishing partner. I appreciated the tips I got. Now I'm in a position to take charter fishing trips instead of working on them. My problem with percentage tipping is that the cost of the trip doesn't necessarily reflect the toil of the guide. Fuel goes up, price of the trip goes up to cover the cost. Is the guide who is putting $1k of fuel in his boat working twice as hard as the guide who put $500 of fuel in his boat? Why would the tip increase?
I also have a negative gut reaction to the "Did you catch anything?" analysis. Some days the fish don't cooperate. If I take my own boat on the river walleye fishing, sometimes I catch fish, but other times I've gotten skunked. My level of competence didn't change. I'm still fishing out of my same boat with my same gear. If I was guiding someone it would suck to add insult to injury by not tipping just because a cold front moved in and the fish had lockjaw.
Reward hardworking effort and good personality.