I don’t eat meat, but Jason’s a pescetarian outside of our house, and he tries to order species that haven’t been overfished. The Monterey Bay Aquarium puts out a good, simple guide that they just updated this month. It’s a good idea to have it in your pocket or on your phone.

Jason uses the sushi guide the most.

A good rule of thumb (in fish as in everything) is to eat farther down the food chain. Large fish like tuna and swordfish are generally more overfished than, say, clams, mussels, oysters, and scallops. Smaller fish are also a good idea for pregnant women or anyone worried about mercury—since larger fish eat smaller fish, they collect and store higher levels of mercury.

But how they’re caught (or farmed) makes a huge difference in the environmental impact. Generally, American or Canadian fish are considered better than imported, in terms of best practices, as well as the obvious carbon footprint of shipping. Maybe they’re just easier to monitor.

Of course, the whole thing is far more complex than this. That’s why we need the Monterey Bay guide and the Marine Stewardship Council label. There’s no way of knowing the impact of every bit of fish you eat (unless you catch it yourself, I guess), but you do what you can.