Thick-lipped grey mullets eat plant material: they graze on algae and seaweed on the sea bottom and on stones, jetties and other solid underwater structures. They will also eat snails. Mullets have relatively long intestinal tracts enabling them to extract most of the nutrients from these barely digestible food sources. They are warm-water fish, common in the southern North Sea from May to October. The thick-lipped grey mullet is the most commonly found species of mullet in Dutch marine waters. It can grow up to 60 centimeters long and is mostly found in harbours where it lives off of the wastes thrown from the ships.