i could be completely wrong but i was under the impression that over fishing (certainly of sea and ocean stock) was a modern phenomenon simply because the sea is so productive compared with historical population densities. The north sea is only in plight today because we scoup out tonnes of fish in huge nets.
That's just plain not right. Overfishing and overhunting have been problems throughout all of history. Not just human history, but all of for animals, as well - populations rise, overgraze or overhunt, kill off their food supply, and start to starve, until their numbers drop low, and the plants or prey numbers start to recover from having less grazers/predators.
Whalers killed off the vast majority of whales without huge nets.
The people of Easter Island are believed to have dissapeared in part because they overtaxed the land, which led to them having to rely on fishing exclusively for their food, and eventually exhausted the fish populations, inflicting famine upon the island, whose remaining population afterwards was not enough to sustain human life on the island.
As long as you are killing more fish than can respawn, you're going to overfish... and if the only limit on population is food, then if you can feed your population now, it will rise, and when it rises, you have to get more food.