Nick Upton / European eel (Anguilla anguilla) elver migrating upstream, using an eel pass on the side of a weir, Somerset Levels, England, UK, July.

Dave Bevan / Male Blackbird (Turdus merula) catching European eel (Anguilla anguilla) elvers as they migrate up a waterfall, Ceredigion, Wales, UK, July.

Dave Bevan / Male Blackbird (Turdus merula) catching European eel (Anguilla anguilla) elvers as they migrate up a waterfall, Ceredigion, Wales, UK, July.

Dave Bevan / European eel (Anguilla anguilla) elvers migrating up a wet rock next to a waterfall, Ceredigion, Wales, UK, July.

Alex Mustard / Giant mottled eel (Anguilla marmorata) in river with villagers washing clothes in background. Ambon, Maluku Archipelago, Indonesia. Banda Sea, tropical west Pacific Ocean.

Juergen Freund / Giant mottled fresh water eels (Anguilla marmorata) in shallows, split level view, Lissenung Island, Kavieng, New Guinea. Second Place in the Portfolio Award of the Terre Sauvage Nature Images Awards...

Shibai Xiao / Marbled eel (Anguilla marmorata) captured by local people and being held up in net, Hainan Island, China. No release available.

Michel Roggo / European Eel (Anguilla anguilla) juveniles migrating upstream, Rhine River, Switzerland, 1992

David Woodfall / Collection of European eels (Anguilla anguilla) bred as part of breeding project, to be exported to Lough Neagh in Northern Ireland. UK. May 2010

Jane Burton / Young European eels / elvers {Anguilla anguilla}, UK

Solvin Zankl / Eel larva in the "leptocephalus" stage {Anguilla sp}, Atlantic ocean

TIM MARTIN / European eel.