At its core, seafood sustainability is about preserving the health and size of the world's fish stock populations. As certain fish species become dangerously overfished, watchdog groups both public and private put out warnings to avoid them. But because populations are ever in flux, it can be hard for shoppers to stay current with the latest recommendations on which fish to buy.

The simplest way to keep up-to-date without hours of research before hitting the market? Handy smartphone apps. Available for free (or close to it), these apps give you the latest lowdown on what's safe to purchase and what to avoid, making it a breeze to navigate the fishmonger's offerings. Here are our two faves:

The Monterey Bay Aquarium's Seafood Watch App (free): Monterey's Seafood Watch is the gold standard for sustainable seafood info. Their app provides up-to-the-minute recommendations, putting seafood in three categories: Best Choices, Good Alternatives, and Avoid. The app also recommends restaurants that serve eco-friendly seafood.

Get Monterey Bay Aquarium's Seafood Watch on Android or iPhone.

Safe Seafood ($0.99): This app aggregates data from various research and advocacy groups to provide a color-coded rating system for more than 100 seafood offerings. Ten percent of proceeds from app sales go to the Environmental Defense Fund.

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