If only “;sustainable”; sushi ordering were as easy as grazing the tabletop nigiri menu: aji yes, bluefin tuna no. But even simple pocket sushi guides being handed out at places like the Maui Ocean Center ask that diners go a step further. It's not just a matter of which species to select, but where and how they were caught.

Ikura (salmon roe), for example, is a fine choice when caught wild in Alaska—the fishery is well managed and most populations there are healthy. Farmed salmon is another story. Raised in crowded coastal pens that can pollute surrounding waters and spread disease to fish in the wild, these salmon and their eggs can contain carcinogens—to the point that the government advises women and children to limit their intake. Sustainability, you see, also has to do also with sustaining the health of humans.

Unfortunately, the upshot of the sushi-guide recommendations comes down to this: Most of the big, beefy, popular ocean fish—tuna, salmon, swordfish, marlin—are no longer sustainable unless caught by hand in the wild.

  Simply put, a fishery is considered sustainable if it can continue its practices without eventually destroying the species or its environment. Not sustainable are large-scale operations that go after high-dollar, open-ocean fish, but also net and kill large numbers of turtles, birds and other species. Nor are fish farms if they pollute waterways, spread disease, overuse antibiotics or deplete the population of juveniles in the wild. Buying from these kinds of operations just gives a thumbs up to putting profits over health, protesters say.

Researchers can't say exactly how much damage bad fishing practices have done in the modern era, but some experts estimate a loss of 80 percent of large ocean species. That's why advocates are looking not only at regulation, enforcement and protection, but also at alerting consumers to outdated notions about the plenitude of fish in the sea.

Kin Lui, who opened the sustainable sushi bar Tataki in San Francisco last year, said he was first moved by an article he read about the endangered bluefin tuna, toro. Ten minutes later he had to go back to his job in a hotel restaurant and serve the prized sushi delicacy.

Lui, 28, grew up on Oahu and spent every summer fishing the North Shore, so when he and his partner, a diver, opened their own sushi bar, they vowed to do no harm. That means there's no farmed salmon, yellowtail, octopus or unagi on their menu.

“;A lot of the most common wet sushi items that most restaurants serve, we have an alternative,”; Lui said from San Francisco. Tataki Sushi offers farmed Arctic char instead of salmon—which has led many diners to discover they prefer it, Lui said.

That is precisely what the publishers of the pocket sushi guides are hoping: that chefs and foodies might persuade the public to try healthier types of sushi that could be equally delicious. “;There's a huge role that the culinary community can play, because they have the ability to make something not normally appealing taste great,”; said Jesse Marsh, fisheries research manager at the Monterey Bay Aquarium, who confessed to only recently discovering the pleasure of raw scallops.

It's not a question of giving up sushi, she emphasized, but of waking up to the fact that “;if everyone wants to eat high-level predators, or things that are popular, like farmed salmon, there are going to be serious consequences—which we are already seeing.”;

With educational partners including the Maui Ocean Center, Blue Ocean Institute and Environmental Defense Fund, the aquarium's Seafood Watch effort hopes diners will start quizzing wait staff and chefs about how and where their fish were caught.

  As hot a topic as sustainability has become on West Coast menus, however, it appears the buzz has yet to reach the sushi-eating capitals of Hawaii or Japan.

Ivy Nagayama, general and managing partner of Sansei Seafood Restaurant & Sushi Bar in Waikiki, said she had not heard of diners or chefs raising questions beyond concerns about seasonal local bans on longline fishing. But if the trend catches on here, “;we will try to adapt,”; she said, “;because ... (sushi) is our concept.”;

Sushi King proprietor Shulee Kondo said her customers generally have only one question: “;They only want to know whether it's fresh or not, that's all.”; Guy Tamashiro said the same of shoppers at his well-known Tamashiro Market.

Nobu Waikiki has definitely heard about the bluefin situation, thanks to a controversy at Nobu London a few months ago. The environmental group Greenpeace revealed that the restaurant was secretly feeding bluefin to its high-end clientele. Now every restaurant in the chain owned by Robert De Niro lists the origin of its tuna on the menu, said Wanloe Konyak Schock, general manager of Nobu Waikiki.

“;Nobu is basically a Japanese restaurant, and most Japanese people like eating the bluefin toro—it's been a part of their diet for years,”; she explained. “;We didn't expect it to be an issue (in Hawaii) because there is a large Asian community here, and they like their sushi and sashimi.”;

  It is the historic indifference of Japanese and other Asian diners to environmental causes that makes the issue a sticky one for the Hawaii fish industry, said Brooks Takenaka, assistant general manager of the United Fishing Agency, which operates the Honolulu fish auction.

Foreign governments might not know or care how their fisheries are managed, which puts domestic suppliers at a disadvantage when calls are raised for greater discrimination, said Takenaka. “;The question is, in areas where it's made a significant issue, Who is going to continue to eat it and who is going to boycott, and what is going to happen in terms of economics?”;

For Taras Grescoe, author of “;Bottomfeeder: How to Eat Ethically in a World of Vanishing Seafood,”; the issue boils down to a few simple maxims. Avoid fish at the top end of the oceanic food chain. Farmed imports, such as shrimp and salmon, also fail to meet good standards, he told Salon.com in April. Instead, look at schooling ocean fish such as sardines, mackerel and anchovies, which have long been popular in Northern Europe and are full of healthy fats. Other good choices are similarly affordable, sustainably farmed species such as oysters, pollock, Arctic char and sablefish (butterfish).

You aren't going to find these items at your favorite revolving sushi counter, of course. If the sushi is relatively cheap, says the Monterey Bay Aquarium's Marsh, chances are it was farmed and/or imported.

Go with the California roll, she advises.

“;And keep asking questions,”; she adds, “;because the more people ask, the more pressure they're under to get that information.”;