I did know at the back of my mind that, of the fish species I can choose to cook for dinner, some are better choices than others ; but I really didn't know which fillet was a better choice for sustainability than the next one. Luckily The Royal Forest and Bird Protection Society of New Zealand does know and has prepared the Best Fish Guide.
The Best Fish Guide lists the fish species available in New Zealand in best choice to worst choice order. Unfortunately no fisheries are actually good choices.
I had bought a selection of fish with which to make a fish soup just before I discovered the guide. I am sad to say that two of the five species I chose were in the Red Worst Choice list : snapper and groper. But the other three were in the Amber Concerns list : trevally, tarakihi and gurnard. I do not think that I will be buying snapper or groper for a long time. It is easy to live without knowing these things but once you find out, and the more you learn, the harder it is to ignore.
Here are links to similar resources around the world, as found on the links page on the Best Fish Guide website :
Australian Marine Conservation Society's Sustainable Seafood Guide
National Audubon Society's Seafood Lover's Guide
Environmental Defense Seafood Selector
National Environment Trust Chilean Sea Bass Animated Movie
Seafood Info Centre
UK Marine Conservation Society's Good Fish Guide