Whole Foods Market Inc. is trying to clear some murky waters for seafood shoppers.

The grocery chain on Monday launched a color-coded rating program – with the help of Monterey Bay Aquarium and Blue Ocean Institute – that measures the environmental impact of its wild-caught seafood.

The program is the latest in a series of moves by major grocers to change seafood policies as concern rises about overfishing and the environmental effects of certain fishing methods.

“There has been a huge increase in attention and energy and enthusiasm (on sustainable seafood) from customers and buyers and fishermen,” said Carrie Brownstein, coordinator of seafood quality standards for Whole Foods.

Similar to a stoplight, seafood is given a green, yellow or red rating. A green rating indicates the species is relatively abundant and is caught in environmentally friendly ways. Yellow means some concerns exist with the species’ status or the methods by which it was caught. And a red rating means the species is suffering from overfishing, or the methods used to catch it harm other marine life or habitats.

Whole Foods said the program complements its wild-caught rating program with the Marine Stewardship Council, a certification program that addresses only a fraction of seafood sold. And it adds to the grocer’s farmed seafood policies, which prohibit antibiotics and sulfates and set other standards.

Target Corp. decided at the beginning of the year to stop carrying farmed salmon. Safeway Inc. stopped carrying overfished species, including grouper and monkfish.

Wal-Mart Stores Inc. dropped swordfish, shark and frozen orange roughy last year after cutting other controversial species previously.

After much pressure from environmental groups, Trader Joe’s announced this spring that it would sell only sustainable-sourced seafood by the end of 2012.

Whole Foods also announced Monday that it will end sales of red-rated species by Earth Day 2013. The company has already phased out a number of such products.

Monterey Bay Aquarium, considered one of the pre-eminent sources on seafood sustainability, developed pocket guides and cards that help consumers navigate the fish counter. It has distributed more than 40 million of the guides and similar cards over the past decade.

By The Associated Press