Their bodies then adapt for the oceanic voyage. The eye enlarges, the gut atrophies, the jaws weaken, and the gonads increase in size. Previously, it took the eels three years to arrive as leptocephalids, carried largely by currents. Now they must combat the same currents. It is not known how long the journey takes, or indeed whether these eels ever succeed in spawning.
Some authorities consider that the migrating European eels never reach their spawning grounds.
They hold the view that the progeny of American mature eels, spawned in the same place, are carried by the currents to renew the contingents of European eels. Other authorities believe that sufficient numbers of the European returners succeed in spawning and so maintain the species. There is still no definite answer to this question. Capacity to survive Perhaps the most surprising characteristic of eels is their capacity to survive out of water for long periods. Anglers know that carp and tench can survive for an hour or two when kept in damp grass, but the eel surpasses them.