Authentication of food products is of ongoing interest to consumers in developed countries. Recently, a general interest in the sustainability of food productions, from both societal and environmental perspectives, developed and added a new dimension. Fish and fish products are common targets for food adulteration. The most important issue is fish management, e.g., the environmental impact of overfishing. Analytical means would be helpful for verification. The aim of the present study was to evaluate various marker groups for the distinction of European plaice from the North Sea from European plaice from other geographical origins: volatile organic compounds (VOCs), fatty acids
(FA), and isotope ratios. VOCs were analyzed using proton transfer reaction mass spectrometry (PTR-MS); the FA composition was analyzed using gas chromatography with a flame ionization detector, and carbon, hydrogen, nitrogen; and sulfur isotope ratios were analyzed using isotope ratio mass spectrometry. In a principal component analysis, FA profiling appeared the best option to distinguish European plaice from the North Sea from those originating from other seas.