Orange roughy is a white-fleshed fish, similar to cod, with a mild flavour, low fat content, and delicate texture. I use it to make Thai fish cakes, and I don't find it fresh in Toronto; I have to buy it frozen. That's because the main fishery for orange roughy is New Zealand, far from my home.
Orange roughy lives not on the surface waters, but in the cold dark depths of the ocean - as much as a mile down. Another interesting factoid I dug up is that they mature in their 30s and can live to be 150 years old or more! A fish! Apparently this is partly due to their habitat, which promotes slow growth and development. This, along with advances in trawling technology, also makes them susceptible to overfishing, and catches have fallen to a fraction of what was harvested a decade ago.