Some Fishpeople are placed on the map during map generation. But the waves of Fishpeople that attack you during a raid are freshly generated - and in the case of the New Antipodia map, they wander in from the ocean, in the direction of the beach. So no, you will never be free of the Fishperson menace.
Well, hang on. If you keep killing them and eating all your eggs it should presumably impact their spawn rate. Any developer comment? There *should* be something you can do - e.g. depth charges.
Current fishpeople behavior isn't really meant to be how it is long-term; rather, it's there to "be interesting" while we flesh out various aspects of economy and combat. Eventually the current "endless waves" system will be replaced with More Interesting Gameplay. So basically, this will eventually be a moot point! XD
