One of my favorite places when I lived in Tokyo was the sushi bar in my neighborhood. I'd take a seat, and the chef would prepare fish fresh from the market in central Tokyo. I liked sushi before I moved to Japan; now I love it. I'm hardly alone, which is bad news for the world's oceans. Partly because more and more sushi is demanded, we're fast fishing out our seas. Some researchers estimate that if we don't change the way we harvest the oceans, all the commercial fisheries (捕鱼业) in the world could disappear as early as 2048. That could mean no more fish to buy in your local supermarket. Fortunately, scientists are looking for ways to fish sustainably (可持续地). One method is a quota system that sets a limited amount to every fisherman or corporation who wants a share of the total catch for certain sea area. These catch shares get rid of the possibility to overfish. A recent study in Science found that the system can pr fishery from dying and even make it better over time. "It's truly a win-win situation," says Steven Gaines, a marine biologist at the University of California at Santa Barbara and one of the study's co-authors. Consumers also can help save the seas through the fish they buy. California's Monterey Bay Aquarium Institute is coming out with pocket guides to sustainable sushi. The researchers base their ratings on the health of a wild fish's population as well as the impacts of fish-farming operations. Oysters, for example, grow fast and can be farmed sustainably, but salmon can't. The researchers also take fishing practices into consideration: catching big-eye tuna (金枪鱼) can cause its nearby fish to die, which certainly no one wants to see. It is hoped that, by the right choice, consumers can encourage businesses to fish in a more sustainable way.