"The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries." The US government deems eels population and the commercial industry was worth $12 million in Maine in 2017. The eel was a cheap, nutritious and readily available food source for the people of London; European eels were once so common in the Thames that nets were set as far upriver as London itself, and eels became a staple for London's poor. The first "Eel Pie & Mash Houses" opened in London in the 18th century, and the oldest surviving shop - M Manze - has been open since 1902.