On the risk of criminal manipulation in caviar trade by intended contamination of caviar with PCR products

The over-exploitation for caviar production has led to drastic decreases of sturgeon stocks worldwide and consequently, all sturgeon species have been listed on the CITES regulation. In order to fulfil the obligation to control caviar trade effectively, species identification can solely be performed by molecular techniques. Here, we show that these approaches are vulnerable towards manipulation and protocols should consider criminal intends to manipulate the caviar. Using artifically amplified DNA (cytochrome b gene) from Acipenser sturio we show, that unsalted eggs and caviar from A. baerii can be manipulated and artificial DNA is detected by DNA sequencing. The amount of PCR product required was determined by a dilution series, and clearly demonstrates that such manipulation is economically feasible as it comprises less than 5% of the actual price. Neither extensive washing nor additional treatment with a non-ionic tensid (0.1 and 0.01% Tween20) unmasked the cytochrome b sequence from A. baerii. Species identity could only be determined successfully by a DNase treatment of contaminated eggs. For a standard testing procedure currently asked for in context of the CITES convention, a DNase treatment should be integrated into the protocol.