Wild or farmed Gilthead Seabream (Sparus aurata)? How to distinguish between them by two-dimensional gel electrophoresis.

As the world wild fish stocks are limited and the market demand increases, fish farming has become an alternative food source and a way to reduce costs for consumers. The sale of farmed as wild fish is a fraudulent practice, it is therefore important to work to provide new and alternative tools that can help in the fight against fraud in order to protect consumers and to ensure food traceability. The proteomic profile of farmed and wild fish differs from one another. With this study we wanted to identify liver protein markers via two-dimensional electrophoresis (2DE) that would allow us to distinguish wild from farmed gilthead seabream.The liver samples from 32 gilthead seabream, wild and farmed, were stored at -80 °C before protein extraction. The samples were subjected to 2DE to detect qualitative and quantitative differences. Proteomic analysis showed a protein spot (molecular weight of ~34 kDa and isoelectric point of ~6.9) only in the samples from the wild gilthead seabream; liquid chromatography tandem mass spectrometry identified the spot as ubiquitin. Ubiquitin could be a valid marker to differentiate wild from farmed gilthead seabream, thus ensuring continuous monitoring throughout the entire commercial chain and fight commercial fraud.