Well, seeing as you brought up the spearfishing topic again, please consider this - a responsible spearfisher ONLY catches what is needed - they target the exact fish they're planning to eat. NO by-catch. No wounded fish with hooks in their digestive track. No undersize specimens. NO by-catch. Did I mention by-catch?
Have you ever eaten a Filet'o'Fish? Ever had fish and chips? Fishfingers? Can of tuna? The catch that caught your meal probably did more damage to the environment than a single spearfisher could inflict in a year (or decade, or lifetime, pick your analogy) of spearfishing.
Sure there's irresponsible idiots (or cast members on Survivor) out there who shoot anything that moves including protected species, but you will find they are by FAR in the minority, and recreational spearfishing doesn't even register as a blip on the annual catch compared to commercial fishing. It is recognised that high intensity spearfishing can be detrimental to local populations, but you will find most spearfishers nowadays are interested in protecting the resources available, unlike in decades gone by when the ocean was considered a bottomless supply of fish that would always be there.
Spearfishing has got to be the most environmentally friendly method available for the collection of wild fish for consumption. Period.