g cover Why chefs are confused about what fish they can serve ‘Sustainability’ has many guises: lists, diner questions, legal restrictions... ← Related Article Visit The Boston Globe Share on Twitter Share on Facebook Comment on this Scroll to top of page Yoon S. Byun/Globe Staff The topic of seafood sustainability has been under discussion so long it’s gone from buzzword to cliché. Here, cod at Area Four in Kendall Square. Yoon S. Byun/Globe Staff Chef Michael Leviton, of Lumiere in West Newton and Area Four in Cambridge, uses the definition of seafood sustainability from the UN. Yoon S. Byun/Globe Staff A hooked Chatham "Tenacious" cod with semolina crust, roasted pot vegetables, and salsa verde, from chef Michael Leviton. Dina Rudick/Globe Staff Fried smelts with meyer lemon and black olive vinaigrette from Rendezvous. Chef and owner Steve Johnson deals daily with the issue of seafood sustainability. Essdras M Suarez/Globe Staff Chef and owner of Island Creek Oyster restaurant at the Commonwealth Hotel, Jeremy Sewall, spoke to a crowd during a class called "Know your Fish." Sheryl Julian/Globe Staff Blue mussels are on the New England Aquarium's approved fish list. Recipe for mussels in white wine with saffron..