Quote Originally Posted by Martin Greywolf View Post
This is a trap. While fish and sea critters do give you some food, it has to make up for the fact that, well, a portion of your available coastline is not arable land. You can't really solve this by being more inland for the same reason you can't farm too far from the city - travelling takes time, and your fishing boat can't really use too many oars to remain profitable.
While a special case (salmon spawning waters), there were a number of high density, non-agrarian, native populations in the north western US that did subsist on mostly fish.

They didn't have cities, but that more reflected the fact that they had no special reason to cluster that extra few miles together.