The fish counter can be an exhausting place as you gape blankly at the fish-counter display, trying to remember: Is it OK to eat tuna twice a week? Is farmed salmon good for me? No more worries. Real Simple asked Tim Fitzgerald, a marine scientist for the Oceans program of the nonprofit organization Environmental Defense, to list the healthiest picks for you — and for the environment.

Click on the above icon to download the Healthy-Seafood Guide — print it out, fold it and put it your pocket. You'll find suggestions for how often to eat the most common fish, based on mercury levels and whether the way they were farmed or caught damages the oceans. (Some fish, like salmon, tuna, and shrimp, appear several times on the list, depending on variety and origin.) If you aren’t sure where your fish comes from, ask the grocer or restaurant waiter.

To get more in-depth info and tips on specific fish, go to www.environmentaldefense.org/seafood.