...and why is that a problem?
Because people like to eat fish.
Look, the main argument in favor of capitalism, once you get outside of objectivist moral theorists (of which I am one, don't get me wrong) is that capitalism delivers abundance. Leonard Peikoff might denounce that as pragmatism, but people from the shanty towns to the boards of directors look only at the bottom line. Whatever it is, be it widgets or fish, capitalism is supposed to deliver more of it at a lower price. If capitalism can't make good on that promise, most people will ditch it in a heartbeat.
For that reason, the ecofreaks would love for everyone to believe that capitalism is all about expoiting resources until they are no good to anyone. I say they're wrong, but you seem to be agreeing with them, except that you tack the words "so what" on the end. I doubt you'll change many minds in favor of a free market approach.