London restaurant serves invasive speciesbr br Silo, a zero-waste restaurant in London, serves invasive species on its menu to promote awareness. Silo's director, Douglas McMaster, finds these ingredients delicious. At a recent dinner, they featured American Signal crayfish, which were introduced in the 1970s as a food source. Unfortunately, these crayfish have harmed the native white claw crayfish, leading to an 80-90 percent decline in their populations in the UK's waterways.