Most people don't realize that buying sustainable fish is not just good for the environment, the future of eating fish, the ocean, and the planet – it's good for your health as well as for the quality of your dinner. "What you want to know [about sustainable fish] is if it's coming from a resource or fishery where it was harvested responsibly without depleting the biomass," says Cimarusti. "We want to tread lightly. If you walk into a shop and buy bluefin tuna as opposed to big-eye tuna that's been harvested from the Pacific, then you're making the wrong choice when it comes to sustainability." The bluefin population is being depleted to a level nearing extinction, he says. But big-eye tuna are less threatened, and even some sushi places selling bluefin may be selling you fish that's less fresh but still pricey because of how hard it is to get. "You want to buy what's wholesome," says Cimarusti. Is the fish world shady? "Yes, it can be," he adds.