"Conger conger - A Conger eel aground".
European congers have an average adult length of 1.5 m (4 ft 11 in), a maximum known length of 3 m (9 ft 10 in), and maximum weigh of roughly 110 kg (240 lb), making them the largest eels in the world by weight, they can be rivaled or marginally exceeded in length by the largest species of moray eel but these tend to be more slender and thus weigh less than the larger congers. Average specimens caught will weigh only 2.5 to 25 kg (5.5 to 55.1 lb). Females, with an average length at sexual maturity of 2 m (6 ft 7 in), are much larger than males, with an average length at sexual maturity of 1.2 m (3 ft 11 in).
When conger eels are between 5 and 15 years old, their bodies undergo a transformation, with the reproductive organs of both males and females increasing in size and the skeleton reducing in mass and the teeth falling out. Conger eels then stop feeding and leave European waters and make the long migration to the subtropical areas of the Atlantic, such as the Sargasso Sea. Once in this area, they spawn, with the female producing 3 to 8 million eggs. Once hatched, the larval conger eels begin to swim back to European waters, where they live until they reach maturity and then begin to migrate to repeat the cycle.