I think the behavior of fishing ships should be changed. Currently, when a fishing ship runs out of visible resources, it either becomes inactive or goes to gather visible resources.
But those visible resources can be from allies, sometimes all the way across the map. On their way there, the fishing ships reveal dozens of other resources, but they still keep sailing to the far side of the map.
Fishing ships should instead become unactive if there are no resources within a range of 20 or 30 tiles.