Just read an excellent, short and direct article,

 "Conning Customer With CO (carbon monoxide)", warning consumers that some seafood processing plants, particularly some in China, use carbon monoxide to extend the fresh look of fish, especially tilapia and tuna beyond its safe "use by" date.  Using carbon monoxide inhibits the fish from changing to a more red or brown color as it ages, which means consumers could believe the fish they're buying is fresher than it actually is.  To read the full article, either click the article title link or photo above.

My next post will provide fish buying tips whether you're buying fresh whole fish, fish steaks or fillets or frozen fish.