Check out which fish and sushi have the most nutrition, have the least environmental contaminants and are the most likely to support sustainability at the Environmental Defense Fund's website (edf.org) and search for "seafood selector".

While people in other countries look for certified sustainable seafood, like fish with Marine Stewardship Council certification, Beijingers may want to select seafood that qualifies as "low".

The "low" concept has two components. The first is to think low on the food chain. Smaller schooling fish with shorter life spans tend to reproduce faster and have lower concentrations of harmful contaminants like mercury.

The second "low" focuses on the natural environment. Eat bottom dwellers such as oysters, mussels and lobster that were raised at sea farms. That way their wild counterparts can continue to clean the ocean and improve water quality.