Yesterday Hawaii fishermen were holding signs on Hawaii roadways to bring attention to the danger of poisoned carbon monoxide treated tuna. It is a tradition in Hawaii to eat sashimi on New Year's Eve. Hence the timely warning.
I did not make the connection on why fresh fish would be treated with CO until I remembered reading in a murder mystery that CO gives a nice pink hue on a person's face before it kills them.
Then it dawned on me that this treatment of the fish was used to give the appearance of a nice red/pink color which to the untrained eye would appeal to the freshness of it. In fact, the fish treated in this matter came from other waters like the Philippines and were frozen, not fresh.
Unfortunately, early that day my husband and I had purchased fresh ahi at our local Japanese market. Upon our return home, we were dismayed to find out that the fish in fact had been CO treated.
Needless to say, I returned the fish and was fortunate enough to find Grade 1 quality ahi tuna at the same market, from Hawaiian waters. You can see by the above pictures the difference between the two fish.
To learn more about carbon monoxide treated fish you can read this article from two years ago or this much olderone.