To attain the latter areas closed to trawling must be allocated. Trawling doesn't necessarily lead to overfishing. Trawl boards and footrope can be rigged to keep the gear off bottom and let certain fish species and sizes to pass to escape underneath. Heavy on deck, the gear loses most of its weight approaching neutral bouyancy while in water. Modern trawl boards represent highly efficient hydrodynamic designs that derive their spreading power rather from water flow than from ground shear.
Wise fishermen try to waste as little power as possible on ground contact.
Some started using foamfilled trawl-boards with a minimum bottom contact. Many codends are designed to keep off bottom, or tend to come off it when filled with fish. Comparative studies on protected areas and trawling grounds might help to find out what really is going on the latter in relation to the former and indicate appropriate management measures. The issue, therefore is not how to leave marine habitats untouched, but how to exploit marine resources intelligently. So, before bustling over every human effect on ecosystem, let's give the issue a honest examination.