American eels spawn in the Sargasso Sea, then currents carry them to various rivers in North America. The larvae are shaped like a willow leaf. Juvenile (yellow eels) colouration varies from yellow to green or olive-brown on the belly and dark on the back. Adults (silver eels) are grey with a white or cream-coloured belly. Adult females may reach up to 1 metre in length and males are smaller, at less than 0.4 metres.