The common or European eel has a very unusual and fascinating life cycle. Adults have long, narrow bodies, with a continuous dorsal, anal and tail-fin (2). The skin is slimy, the lower jaw is longer than the upper jaw, and the scales are tiny or absent (2). The colour of adults depends on their age; they are often brown, black or olive-green with yellowish bellies. Some adults may be silvery (known as 'silver eels'); the lifecycle stages differ greatly in appearance (2).