There are plenty of fish in the sea, right? Not for some species. To spread awareness of the environmental ramifications of the seafood it peddles, Whole Foods Market (Nasdaq: WFMI) has launched a rating system for its fin-bearing fare.

Whole Foods developed its color-coded ratings in conjunction with Monterey Bay Aquarium and Blue Ocean Institute. Green represents the environmental "best choice." Yellow indicates that despite concerns with fishing methods, this species is still a "good alternative." Red urges customers to "avoid" a purchase, because the species is overfished or the fishing methods are environmentally detrimental.

In addition to the rating system, Whole Foods pledged to discontinue selling the red-rated seafood by Earth Day 2013. It also said it's the first national retailer to offer such a ratings program for its seafood.

Enough consumers care about such issues to convince retailers such as Target (NYSE: TGT), Safeway (NYSE: SWY), and Wal-Mart (NYSE: WMT) to respond. They're pursuing more sustainable fishing policies, and/or discontinuing farmed salmon or overfished species such as swordfish and shark. Trader Joe's has pledged to offer only sustainably sourced seafood by 2012, after being targeted by Greenpeace. Costco (Nasdaq: COST) has been the subject of a similar campaign for selling some "destructively farmed" species.

This sustainability initiative is an important component of Whole Foods' brand. Focusing on awareness and consumer education is one of Whole Foods' competitive advantages, and the company touted its ratings system as a way to empower shoppers in their seafood choices and drum up consumer goodwill. Shareholders should feel gratified that Whole Foods differentiates itself -- and strives to be more than "just a grocery store" -- by remaining true to its lofty purpose with policies like this one.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.