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. I caught a 15cm T.L. elver in a river estuary in S.W. England. The sex an eel becomes is partly determined by environmental conditions such as crowding and food abundance. In areas where food abundance and water temperatures favour rapid growth rates, a higher percentage of male eels are found. The next problem was where to keep him.