That's rediculous. They can't tell you what to do - you are the customer - stand your ground. You could try mentioning to them that you will let them know what your final count was at the end so they can add it to their numbers - that has worked for me.

Also, it is illegal for one guy to catch more fish than his limit by having them count toward another person's limit. If there was an undercover warden on the boat the angler would get the ticket.