Byzantine supply chains, frequent bycatch, brand naming, species substitution, and inaccurate ecolabels all contribute to confusion for the consumer. A 2013 study by Oceana found that one third of seafood sampled from the United States was incorrectly labelled. Snapper and tuna were particularly susceptible to mislabelling, and seafood substitution was the most common type of fraud. Another type of mislabelling is short-weighting, where practices such as overglazing or soaking can misleadingly increase the apparent weight of the fish. For supermarket shoppers, many seafood products are unrecognizable fillets. Without sophisticated DNA testing, there is no foolproof method to identify a fish species without their head, skin, and fins. This creates easy opportunities to substitute cheap products for expensive ones, a form of economic fraud.