In most cases if I am going fishing in somebody elses rig I offer to pay for launch, bait or what ever else. Most of the time my offer is declined and the person says I was going anyway.
If I OFFER to take someone out in a boat I never ask them for money as I OFFERED to take them fishing. If they try to pony up I respectively decline the cash because as stated above, I was going fishing anyways wether they showed up or not.
NOW if someone calls you and asks you to take them fishing and you hadnt planned on going that might be the 1 and only time accepting some kind of offer would be in order.
Maybe letting people know before getting them into your boat that you are expecting some kind of $ or donation then they would be better at coughing up some cash. But dont call them and OFFER to bring them out while in the back of your mind you are EXPECTING them to pay, if thats the case dont offer.
A trip of more than 50 miles from home needs to be planned accordingly and the costs of fuel, lodging and whatever else should be discussed prior to leaving for the venture and split evenly. Just my 2 cents