Mmm. That's great bass. But is it sustainable?Photo: Norm EvangelistaThe international seafood labeling organization, Marine Stewardship Council (MSC) got some boat-rocking news last week, when researchers discovered that a significant portion of what had been labeled MSC-certified Chilean sea bass was in fact something else. Chilean sea bass, also known as Patagonian toothfish, became enormously popular in the last decade because of its flaky texture and light, buttery taste. But pressure on the slow-growing species made it especially vulnerable to overfishing. Today, the fish tops the red "avoid" category on the Monterey Bay Aquarium's Seafood Watch list. But, as is …