Anguilla anguilla, the European eel. Some years ago, the Best In Show prize at a major British fishkeeping event was won by a magnificent European eel. This was enough to relight an interest I have had in this fascinating species since childhood.
Eels have a fascinating life history.
Eventually, these enter rivers, attracted by freshwater discharge. Unlike salmon, eels do not automatically return to the same rivers as their parents. In brackish estuaries, the young eels start to gain external olive-green pigment and are then known as elvers . Some elvers remain in estuaries, but most migrate inland and mature into adult eels. The move to freshwater is accompanied by another change - darker pigment above, white below.