[ghoerz]

The issue with having individual fishing companies determining policies is that it invokes the tragedy of the commons. http://en.wikipedia.org/wiki/Tragedy_of_the_commons

This is addressed in part by the Law of the Sea Treaty, but this only addresses waters out to 200 nautical miles. http://en.wikipedia.org/wiki/Law_of_the_Sea_Treaty

Living resources past this zone are free game. If any fishing companies pull out of a region to allow the populations to grow, it only opens up opportunities for other companies to come in.