Restaurateurs have been urged to avoid using bluefin tuna, after research revealed that stocks of the fish had plunged dramatically over the past decade.
The report, by global conservation organisation WWF, found that bluefin tuna stocks in Mediterranean fishing grounds are down 85% compared with 1996.
It also suggested that tuna farms in the region have experienced a substantial decline and a number of ranches have shut down as a result.
In response to the report, UK sushi chain Moshi Moshi, which has outlets in Brighton, Liverpool and London, has taken the fish off its menu.
"If we continue to eat bluefin tuna, soon there will be none left," said founder and owner Caroline Bennett. "We have replaced it with yellowfin tuna in all of our restaurants and although its meat isn't as fatty as bluefin, none of our customers has complained."
Robin Rowland, chief executive of Yo! Sushi, said fishing bluefin tuna in the Mediterranean was unsustainable.
"We never have and never will use bluefin tuna and instead use yellowfin from the Maldives or Sri Lanka," he said. "Anyone fishing bluefin tuna in the Mediterranean is fishing from a very depleted stock and it's simply not sustainable."
Michael Radtke, executive chef at the Novotel hotel in London Tower Bridge, said he used Mediterranean bluefin tuna only when it is available as a result of a by-catch but would not order it.
"I usually source bluefin tuna from Australia, where there are sustainable stocks," he said. "People must understand that we have to steer clear of endangered species to keep stocks in circulation. Just like cod, Mediterranean bluefin tuna is a species that needs to be protected."