Recent estimations categorize about 37% of all cartilaginous fish species (sharks, rays and chimaeras) as endangered. Especially sharks show severe population declines and many species are protected by CITES and other international conventions. Shark meat and other body parts are sold as various products internationally, often via complex trade routes. As most shark products (like cartilage pills, liver oil or smoked meat) are heavily processed, correct species identification can only be achieved via DNA-based methods. It has been shown that a large proportion of shark products ends up mislabelled to the consumer in Europe. Moreover, fraudulent and economically motivated substitution with cheaper meat is a strong driver for illegal and non-transparent shark trade. Interestingly, the German market is one of the most significant key drivers of the legal trade with Squalus acanthias, the spiny dogfish, which is appreciated in gastronomy as ‘Schillerlocken’ although the species is listed as vulnerable by the IUCN. Additionally, cartilage pills are a popular ‘health’ product in ‘alternative medicine’. We wanted to find out whether mislabelled and substituted shark products exist in the German market. Hence seven ‘Schillerlocken’ and 17 products of ‘shark cartilage pills’ were analysed by DNA-Barcoding. We used various primer cocktails to amplify and sequence between 127 bp (‘minibarcodes’) and 650 bp of the mitochondrial Cytochrome C Oxidase subunit I. We identified 45.8% Squalus acanthias (including all ‘Schillerlocken’) and 8.3% critically endangered shark species (Galeorhinus galeus), as well as 4.2% Prionace glauca. In addition, we report 70.6% of the cartilage pills as mislabelled or substituted. The analysis revealed the use of an undeclared teleost species (Merluccius merluccius, European hake), as well as Gallus gallus (chicken) and Solanum sp. (potato). Our results support earlier demands for better transparency and stronger regulation of the shark product market and hold implications for conservation as well as for consumers' health.

DNA was extracted from either fermented shark abdominal flaps or shark cartilage food supplements (N=23). PCRs were conducted targeting between 127 and 650 bp of the mitochondrial Cytochrome C Oxidase subunit I. Sequences were obtained by Sanger sequencing.