Mislabelling occurs when a fish species is labelled incorrectly before being sold. This occurs more frequently for fish species that are more expensive. The estimated cost of substitution within fish markets is about $24 billion worldwide. The researchers worked with investigative reporters to buy fish samples from places where people shop for fish every day, and found that mislabelling is systemic across Canada. This has implications for health and consumer choices to choose sustainable fish products. This study also found that DNA barcoding is an excellent tool to identify fish species, although more work is needed to identify all fish species.