What is supposed to be being "saved" here? If a fisherman unknowingly destroys an object that nobody else ever knew was there, what's the loss?
Ben Haskell try to preserve those marine sanctuaries by asking politely to stop, hoping fishermen love to marine life may restrain them for destroy it.
Reefs can't be fishing-protected areas because of the presence of fish. The presence of fish is how we pick fishing-intensive areas.
Not. Complex problems don't have simple answers.
We don't define fisheries by the presence of fish. We define fisheries by the presence of fish that --can be-- fished. This means normally age, not number. And age can't be measured easily in many species so we use size instead. Distance to the coast, population status and life cycle are also hugely influential.