Although many Dutch restaurants claim to cook fish from sustainable sources, a majority still sell fish which is not environmentally responsible to eat, according to research by the Good Fish Foundation.

Research into the menus of 500 restaurants claiming to sell fish from sustainable supplies found that 81% had at least one item on the menu which does not meet that description.

Of those, 30% had two red-flagged species on their menu and one in five had three or more. The foundation flags a fish as red if they are farmed using polluting methods, if they are endangered and if fishing techniques damage the sea bed.

The most common red flag fish are giant prawns, or gambas, which are widely farmed in Asia. Fresh tuna, usually yellow fin, was on one third of menus while eel, a seriously endangered European species, was on 15% of the menus.

Four in five chefs told the foundation in a phone interview that they considered sustainability to be very important.

‘These chefs want to be responsible but they don’t have enough expertise or information,’ foundation director Christien Absil said. ‘And most suppliers are not clear about what sustainable fish they are selling either.’