A variety of Scorpion Fish particularly adapted to the deep "oxygen minimum" layer of the ocean where most fish can not thrive. It has a huge head, both long and wide, housing very large gills. It lives in the North Pacific, some as far south as the Mexican border but mostly Northern California, Washington State, Canada and Russia, but as far south as northern Japan. This fish can grow to 31 inches and 20 pounds but the photo specimen was 21 inches and 4-3/4 pounds, towards the large end of market size.
Living under very sub-optimal conditions the Idiot Fish grows slowly and has a slow propagation rate. The U.S. fishery is tightly regulated under Federal fisheries programs to avoid overfishing, consequently it's not found far from the Pacific coast. Of course it's strange spiny appearance is sort of off-putting for many people anyway, which is just as it should be because there will be more for me. Outside the U.S. Pacific coast regulation may be deficient and the IUCN Red List status is EN (Endangered) due to its slow propagation.
More on Rockfish.
Idiot flesh is very tender and very white, with a fairly thick darker layer under the skin. The darker layer does not have a strong flavor but it is different in texture - being a bit gelatinous it does not flake at all. This would help hold chunks together if used in soup. The rest of the flesh is also slightly gelatinous and breaks apart as much as it flakes. All in all, Idiot has a subtle but interesting flavor, particularly when poached, and is sweeter than other rockfish.
Buying: Idiot Fish can often be found in Asian markets in Los Angeles, though I don't remember seeing it in those that serve a primarily Philippine community. It is a premium fish, selling for US $4.69 and higher for whole fish.
Scales: Idiot Fish is covered with small thin scales that scrape off easily and do not fly about at all.
Cleaning: There's a lot of stuff inside one of these, and up at the head end it won't pull so you need to cut it off with kitchen shears. The gills are huge, have prickly gill rakers and are strongly attached. You'll need to cut them out with kitchen shears.
Fillet: The Idiot Fish is fairly easy to fillet, though its limpness does cause a little trouble. First cut off the head, turing the knife steeply under the gill covers to get the maximum amount of flesh. When I get to the ribcage I cut the ribs loose from the backbone with kitchen shears and pull them from the fillet with long nose pliers. There are a few substantial centerline spines up near the front of the fish that need to be pulled.
Yield: Yield is moderate due to the huge head and heavy bones. A 4-3/4 pound fish yielded 1 pound 11-3/8 ounces of skin-on fillets (36%) and 1 pound 9-7/8 ounces skin-off (34%). There will still be a lot of flesh on the carcass, particularly the collar, which can not be removed except after a short simmer.
Skin: The Idiot Fish's skin shrinks severely when cooked so it should be removed for any method of cooking. It is very thin but tough and fairly easy to remove using the standard long knife and cutting board method. Very little flesh should be lost.
Cooking: Due to the huge head and severe skin shrink this fish is not suitable for cooking whole. Fillets can be pan fried or poached and hold together very well. Like other rockfish, Idiot will curl a bit to the skin side, even though the skin has been removed. When poaching it is best to cut the fillet in half lengthwise so the pieces are long rather than wide. This is a good fish for cutting into chunks for fish soup as the chunks will hold together well.
Stock: The head, fins and bones make a medium flavored fish stock suitable for soups and stews, and because the head is huge and fleshy it will make quite a bit of stock. The stock does have a fair amount of oil which needs to be separated out - use your gravy separator. When you start making stock make sure you have plenty of water and bring to a boil uncovered. A large amount of slime and foam will rise to the surface as it comes to a boil - remove it with a skimmer.