Jessica Levy, Dallas senior, eats sushi two to five times each month. Her favorite restaurant is Yokohama Sushi and her favorite food is the Rookie Roll: Spicy crab with cucumber, topped with avocado. She also loves spicy tuna, and has lately been ordering a lot of rolls with eel.

Levy says she orders her rolls based on taste.

But students could now find that some fish leave a bad taste in their mouths because of environmental factors. The Blue Ocean Institute, a national conservation organization, recently released a guide on how to make sure the sushi on your plate is sustainable. The guide ranks the environmental friendliness of fish based on farming and catching methods, the risk of overfishing and health concerns. A green ranking is the best, followed by yellow-green, yellow, orange and red for worst.

While Levy said the environment didn’t usually enter her mind when looking at the menu, she said she’d consider changing her ways.

“If I had the information in front of me, I would definitely try to make better choices on which fish I eat,” Levy said.

Students can print a pocket-sized sushi guide at www.blueoceaninstitute.org. Students can ask their favorite sushi chef what kind of fish is used in his restaurant, and then base orders off sustainability and taste.

The best and worst of tuna

Skipjack tuna, called Katsuo on menus, is one of the most ocean-friendly tuna varieties according to the guide. They breed quickly and are more abundant than other tuna populations. Albacore tuna, called Bin’naga maguro, is another good variety. Like the skipjack, it has a high reproduction rate and is found easily in tropical waters. But the sushi guide emphasizes the importance of knowing how the fish is caught. Albacore is sometimes longline caught, a process that can often snag and kill seabirds, sea turtles, sharks and other fish by accident.

Hla Moe, sushi chef for Sushi with Gusto at the Underground, said he uses albacore or bluefin tuna, depending on what’s available.

Kokoro, 601 Kasold Drive, and Yokohama Sushi, 811 New Hampshire St., use mostly bluefin tuna, one of the worst-rated fish on the sushi guide. The bluefin population is extremely endangered and has been overfished in most oceans, according to the pocket guide. Bluefin tuna can also contain levels of mercury or Polychlorinated Biphenyls, PCBs, that could pose potential health risks.

Kevin Shin, owner of Kokoro, said tuna and salmon were the most popular fish ordered in his restaurant. He said he was aware of some of the risks in certain types of tuna, but said he didn’t think Kokoro received any dangerous varieties in its shipments.

The best and worst of salmon

Wild Alaskan salmon is the top-rated fish on the sushi guide. The wild salmon comes from a fairly clean and healthy habitat, and is certified sustainable by the Marine Stewardship Council. Wa, 740 Massachussetts St., uses wild salmon imported from Scotland, which is not a place mentioned in the sushi guide. Sushi with Gusto, the sushi offered at the Underground and in the Union, uses only wild salmon. Yokohama Sushi uses farm-raised salmon. Along with bluefin tuna, farm-raised salmon is one of the worst-rated fish on the guide. The sushi guide says salmon farming pollutes ocean waters and can spread disease to wild fish in the areas near salmon farms. The guide says all Atlantic salmon sold in the U.S. is farmed. Shin said Kokoro carried wild and farm-raised salmon, depending on the market.

The best and the worst of Mackerel

Mackerel, called Saba on menus, is given a green ranking on the guide. Mackerel produce a lot of offspring, allowing for an abundant population of the fish.

Spanish mackerel, called Sawara on menus, has the same positive points as Saba. But Spanish mackerel has shown to have levels of mercury or PCBs that could prove dangerous according to the sushi guide.

More of the worst

Red snapper, which is served at Wa, Yokohama, Kokoro and Kobe, 2907 W. 6th St., received a red rating on the guide. These fish grow and reproduce slowly and have long life spans, making it easy for populations to be overfished. Freshwater eel, called Unagi on menus, is served at Wa, Yokohama, Kokoro, Kobe, the Union and the Underground. Eel was given a red ranking on the guide for the way it is farm-raised. Eels are usually farmed in pens that can cause serious environmental damage because of the untreated eel waste. Eels are also carnivorous, and require a diet of many other fish. Populations of wild eel are declining because eels are often caught while young and put into farming pens.

— — Edited by Susan Melgren