Illegal fishing endangers many fish species. But fishing is notoriously hard to track and control. However, the blockchain technology first used to power the currency Bitcoin, has now been tested to track fish from trawler to the supermarket in a breakthrough that could help stop human rights abuses and illegal fishing. Blockchain is a digital ledger or record of information that is accessible to everyone. In this case, it details the origins of fish and allows anyone to see where the fish was caught, processed and sold on. It does not stop illegal fishing on its own but it opens up the supply chain for anyone to scrutinize. Delivering transparency will change public opinion and consumer behavior.