Retailer's roles in rescuing the world's favourite fish. Global tuna stocks are in big trouble. Tuna is one of the world’s favourite fish, the staple protein in the diet of millions, and the fish at the core of the luxury sashimi market. Perhaps the best known example is the Southern Bluefin Tuna. Since industrial scale fishing of southern bluefin tuna began in the 1950s, the biomass of reproducing fish has been reduced by some 95% and the species was listed as endangered by the IUCN in 1996 . The depletion of the other major global tuna stocks has been recorded by fisheries scientists over many years. Today, there is the real possibility that commercial extinction is imminent for some stocks of these valuable and iconic species.