Principially you're right: We should not just applaude a yearly market share increase of sustainable labelled seafood - we have to improve fishery practices all over the place, by joint efforts of producers, consumers, retailers, governments and NOGs. But this is a long and tedious way to go, and its always helpful to start with some good steps which pilot tasks to be performed.
Eco-labelling can be one of these first steps, provided that a label keeps its promises. It's here that we have a problem actually. The leading sustainability label on the market provides seafood originating from already overfished species, like Alaska Pollock, or gained by methods severely destroying the marine environment, like bottom trawling. It is no surprise then that New Zealand's authorities had to cut in half the total allowable catch (TAC) for Hoki ever since fisheries on these stocks had been certified against MSC standards in 2001 (see graph below).
Consumers would suggest that WWF's label MSC does replace methods which plough the seabed, generate high bycatch and burn lots of fuel. They will be very confused when they learn that nothing has been changed at all, and consequently they'll be lost as partners for a real change. Without consumer's pressure, retailers will resign, too, and in the end the industry will be left alone again. In its own interest, the seafood industry should urge MSC to adopt much stricter criteria. Opting for Friend of the Sea would be a very direct way to make it plain to MSC. It's just about saving the first good steps before we can ever think of coping with the task you mentionned.
Dear Drew Cherry