Rockfish is an umbrella category for a group of slow-growing fish that reside in salt water, spawn in fresh water, have poisonous spines and can live upwards of 100 years. The 100 or more species of rockfish fall into two subcategories: pelagic (shallow, open waters) or non-pelagic (deep waters, bottom feeding). Striped bass is the only official rockfish species in the Atlantic Ocean. Examples of Pacific rockfish are black, yelloweye and quillback. As a delicacy, these fish are firm-fleshed with a mild flavor that lends well to deep frying, pan frying and sushi or ceviche (marinated in lime). Before you select rockfish for home sushi preparation, you should heed certain precautions.
Buy sushi-grade rockfish. Fish sold in supermarkets are usually a lower grade, may harbor parasites or bacteria and are generally not safe for use in sushi. According to the Sushi FAQ website, sushi-grade fish once reserved for restaurants are now available to the public through many fish markets. Ask your fish market if it carries sushi-grade rockfish.
Ask your fish market where it purchases its rockfish supply. Ninety percent of the striped bass variety of rockfish comes from the Chesapeake Bay area and its tributaries. In 2000, 60 percent of the Chesapeake Bay was infected with mycobacteriosis, a "wasting-away" disease that causes inflammation, tissue destruction and buildup of scar tissue in the fish. Infection is not visible from the outside, and it's not known how many fish die or recover from the disease. However, it is transmittable to humans through handling (fish-handlers disease) and by eating raw or improperly cooked rockfish. The Maryland Department of Health and Mental Hygiene discourages anyone from eating raw rockfish fished from that area.
Ask the fish market to clean and fillet your rockfish. According to "A Healthy Me," a publication put out by Blue Cross Blue Shield of Massachusetts, eating raw fish carries inherent risks for worms and parasites. Despite the popularity of sushi in the United States, most parasite infections don't occur from eating professionally prepared sushi; they occur from improper handling and preparation of home-made sushi. It's easier for you or your fish market to inspect a fish for worms or larvae if filleted. In addition, some species like the China rockfish have poisonous spines and though not fatal, can be mildly painful if touched. If you're a novice at preparing and cleaning rockfish, leave the job to your fish market.
Inspect your fish fillet by holding it up to a lightbulb. Or, ask your fish market if it "candled" the fish before selling it. If larvae or worms are present in the flesh, candling will show them through the translucent fillets. Unlike the natural granulation of a fish musculature, worm larvae are bright white. In addition, inspect your fish for red lesions, usually a sign of illness or infection.
Use fresh-frozen rockfish for sushi. Sushi FAQ claims that most fresh fish is "flash frozen" or frozen quickly. Freezing fish kills any worms or larvae, and dead parasites are harmless if consumed. Commercial facilities freeze fish at much lower temperatures than your home freezer; consequently, there is a higher probability that sushi-grade fish you buy is safer than any you might freeze at home. Because it's difficult to assess the quality and freshness of commercially packaged rockfish, don't use it in sushi.
Disinfect all utensils, surfaces and your hands. In addition to introducing illness-inducing bacteria into the sushi, unclean surfaces can alter the flavor of the fish. Many recipes calling for raw rockfish recommend using it in a ceviche or lime-juice marinade. Though lime or lemon juice doesn't kill parasites, it does act as a preservative. Slice fish fillets across the grain and use as thin slices or matchstick pieces in your sushi rolls.
Do not use freshwater fish in sushi. Some bacteria and parasites that live in freshwater fish are more harmful than the saltwater variety.