Once a fish is skinned and fileted, you can’t tell species apart, you have to trust the vendor.
But 39% of 142 samples from 81 retail outlets in New York City were not what the label said, and similar results occurred in Boston, Los Angeles, And Miami. according to a December 2012 Oceana study (a conservation organization in Washington D.C.).
“White tuna” is often substituted with escolar (Lepidocyblum flavorbrunneum). Eating more than 3 ounces of this causes severe diarrhoea. 94% of “white tuna” in Oceana’s study was escolar.