Anything extra is nice as a captain, especially since most of us try to keep cost down so everyone can enjoy a day on the water. A couple jets lost, along with a spoon or rr can add up fast, a net overboard is a fast debt also. A gesture such as being tiped as a captain goes along way and is always remembered for the next trip.
Now the first mates really work for tips (15-20% ish) of trip cost, they are there to make trip easier an more enjoyable for the clients. I myself will give my first mate a little extra, since I myself was there, and still do help out on some other charters when Im not running one. Enjoy your fishing day on water- ron