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.

David Fleetham / White-eyed moray eel (Muraena thyrsoides) close to Zebra lionfish (Dendrochirus zebra), Philippines.

David Fleetham / Pair of White-eyed moray eels (Muraena thyrsoides) share the hole of a mooring block off Bali, Indonesia.

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.

Franco Banfi / Green moray (Gymnothorax funebris) Santa Lucia, Camaguey, Cuba, Caribbean Sea, Atlantic 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...

Alex Mustard / Group of predators hunting together, in an example of 'Nuclear foraging'. The Moray eel (Gymnothorax javanicus) flushes out prey, and is followed by a Napolean wrasse (Cheilinus undulatus) and a Bluef...

Alex Mustard,Alex Mustard / Portrait of a Yellow moray eel (Gymnothorax prasinus) - endemic to SE Australia. Chowder Bay, Sydney Harbour, New South Wales, Australia.

Wild Wonders of Europe / Lundgren / Marbled moray (Muraena helena) coming through hole with mouth open, Princesa Alice, Azores, Portugal, June 2009

Wild Wonders of Europe / Lundgren / Marbled moray (Muraena helena) with mouth open, Princesa Alice, Azores, Portugal, June 2009

Wild Wonders of Europe / Lundgren / Black moray (Muraena augusti) with mouth open, Pico and Faial, Azores, Portugal, June 2009 WWE BOOK

Wild Wonders of Europe / Banfi / Moray eel (Muraena helena) looking out of a hole in the artificial reef, Larvotto Marine Reserve, Monaco, Mediterranean Sea, July 2009

Wild Wonders of Europe / Banfi / Moray eel (Muraena helena) looking out from a hole in the artificial reef, Larvotto Marine Reserve, Monaco, Mediterranean Sea, July 2009

Wild Wonders of Europe / Banfi / Moray eel (Muraena helena) looking out of a hole in the artificial reef, Larvotto Marine Reserve, Monaco, Mediterranean Sea, July 2009. WWE INDOOR EXHIBITION

Wild Wonders of Europe / Zankl / Mediterranean moray eel (Muraena helena) Malta, Mediteranean, June 2009

Pascal Kobeh / Goldentail moray (Gymnothorax miliaris) Cozumel Island, Yucatan peninsula, Mexico.

Shane Gross / Goldentail moray eel (Gymnothorax miliaris) with mouth open, close up. Eleuthera, Bahamas.

SCOTLAND: The Big Picture / European eel (Anguilla anguilla) migrating upstream bypassing a waterfall by leaving the water completely. Cairngorms National Park, Scotland, UK, July.

Alex Mustard / Three moray eels, a Honeycomb moray: (Gymnothorax favagineus), Yellowmargin moray: (Gymnothorax flavimarginatus) and White-eyed moray (Gymnothorax thrysoideus) emerge from a single hole in a coral ree...

Georgette Douwma / Whitemouth moray eel (Gymnothorax meleagris). Lembeh Strait, North Sulawesi, Indonesia. Indo-Pacific.

Juergen Freund / Snowflake moray eel (Echidna nebulosa) peeping from inside a discarded ghost net on a coral reef, Sulawesi, Indonesia. November.

Pascal Kobeh / Greyface or White-eyed moray eel (Gymnothorax thyrsoideus / Siderea thyrsoidea) Sulu Sea, Philippines

Pascal Kobeh / Mediterranean moray eel (Muraena helena) Azores, Atlantic Ocean.

Pascal Kobeh / Mediterranean moray eel (Muraena helena) Azores, Atlantic Ocean.

Pascal Kobeh / Mediterranean moray eel (Muraena helena) Azores, Atlantic Ocean.

Pascal Kobeh / Duke Augustus moray eel (Muraena augusti) Azores, Atlantic Ocean.

Pascal Kobeh / Duke Augustus moray (Muraena augusti) Azores, Atlantic Ocean.

Pascal Kobeh / Duke Augustus morayeel (Muraena augusti) Azores, Atlantic Ocean.

Dave Bevan / European eel (Anguilla anguilla) elvers migrating up a rock face next to a stream, 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) elver trying to migrate up a rock face, before slipping back, 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 / Pair of a Honeycomb moray eels (Gymnothorax favagineus) on a coral reef with triggerfish schooling above. North Male Atoll, Maldives, Indian Ocean.

Alex Mustard / Shallow depth of field portrait of a White-eyed moray (Siderea thysoidea). Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Magnus Lundgren / Wild Wonders of China / Richardson's moray (Gymnothorax richardsonii) Shelter Island, Sai Kung archipelago, Hong Kong, China.

Remi Masson / European eel (Anguilla anguilla) in the River Rhone, Alps, France. Critically endangered species.

Jean E. Roche / Fishermen carrying net of live Eels (Anguilla anguilla) Camargue, France, November.

Jean E. Roche / Fishermen carrying net of live Eels (Anguilla anguilla) Camargue, France, November.

David Fleetham / Snowflake moray eel (Echidna nebulosa) passing in front of these two Green sea turtles (Chelonia mydas) an endangered species, off Maui, Hawaii.

David Fleetham / Whitemouth moray eel (Gymnothorax meleagris) showing the curved teeth in the upper jaw for holding prey, Hawaii.

David Fleetham / Yellowmargin moray eel (Gymnothorax flavimarginatus) with a Banded coral shrimp (Stenopus hispidus) inspecting it for parasites, Hawaii.

Alex Mustard / Giant moray (Gymnothorax javanicus), Honeycomb moray (Gymnothorax favagineus) and Undulated moray (Gymnothorax undulatus) eels, four emerging from hole in coral reef. North Male Atoll, Maldives. India...

Alex Mustard / Honeycomb moray (Gymnothorax favagineus) on coral reef with Triggerfish (Balistidae) schooling above. North Male Atoll, Maldives. Indian Ocean.

Linda Pitkin / Bluefin trevally (Caranx melampygus) mixed-species foraging and hunting behaviour, with Giant moray (Gymnothorax javanicus). Shark Reef to Jolande, Ras Mohammed National Park, Egypt, Red Sea.

Linda Pitkin / Undulated moray (Gymnothorax undulatus) The Barge wreck, near Bluff Point, Gubal I., Gulf of Suez, Egypt, Red Sea.

Linda Pitkin / Undulated moray (Gymnothorax undulatus) The Barge wreck, near Bluff Point, Gubal I., Gulf of Suez, Egypt, Red Sea.

Linda Pitkin / Goldentail moray (Gymnothorax miliaris) Bonaire, Leeward Antilles, Caribbean.

Claudio Contreras / Jewel moray (Muraena lentiginosa), El Violin, Huatulco Bays National Park, southern Mexico, November

Jordi Chias / Honeycomb moray eel (Gymnothorax favagineus) under coral, Mozambique

Jordi Chias / Laced moray (Gymnothorax favagineus), Ari atoll, Maldives islands, Indian Ocean

Jordi Chias / Laced moray (Gymnothorax favagineus), Ari atoll, Maldives islands, Indian Ocean.

Georgette Douwma / Two Snowflake moray eel (Echidna nebulosa) Ambon, Indonesia.

Georgette Douwma / Two Greyface moray eels (Gymnothorax thyrosoideus) Ambon, Indonesia.

Georgette Douwma / Three Greyface moray eels (Gymnothorax thyrosoideus) Ambon, Indonesia.

Georgette Douwma / Snowflake moray eel (Echidna nebulosa) Ambon, Indonesia.

Georgette Douwma / Snowflake moray eel (Echidna nebulosa). Ambon, Indonesia.

Georgette Douwma / Giant moray eel (Gymnothorax javanicus). Ambon, Indonesia.

Georgette Douwma / Snowflake moray eels (Echidna nebulosa) with plastic on the sea floor, Ambon, Indonesia.

Alex Mustard / Snowflake moray eel (Echidna nebulosa) home amongst garbage on the seafloor, including a plastic toothpaste tube. Ambon Bay, Ambon, Maluku Archipelago, Indonesia. Banda Sea, tropical west Pacific Ocea...

Alex Mustard / Latticetail moray (Gymnothorax buroensis) emerging from soft coral on a reef. Sangeang Island, Sumbawa, Indonesia. Flores Sea.

Jean E. Roche / European eel (Anguilla anguilla) portrait, Camargue, France.

Jean E. Roche / Trapping European eels (Anguila anguilla) in the Camargue, for scientific research by the biological research station of Tour du Vala.

Jean E. Roche / European eels (Anguilla anguilla) released after scientific research, La Gacholle, Camargue, France. April.

Jean E. Roche / Scientists releasing European eel (Anguilla anguilla) after they were caught during research, La Gacholle, Camargue, France. April.

Jean E. Roche / Scientists measuring European eels (Anguilla anguilla) during research, La Gacholle. Camargue, France, April.

Georgette Douwma / Giant moray eel (Gymnothorax javaniucus) hunting over coral reef, Red Sea, Egypt. January.

Franco Banfi / Yellowmargin moray (Gymnothorax flavimarginatus) peering out of hole, Tubbataha Reef Natural Park, UNESCO World Heritage Site, Sulu Sea, Cagayancillo, Palawan, Philippines

Franco Banfi / Fine spotted moray (Gymnothorax dovi) Malpelo Island National Park, UNESCO World Heritage Site, Colombia, East Pacific Ocean

Franco Banfi / Fine spotted moray (Gymnothorax dovii) Malpelo Island National Park, UNESCO World Heritage Site, Colombia, East Pacific Ocean

Franco Banfi / Fine spotted moray eels (Gymnothorax dovi) together in den, Malpelo Island National Park, UNESCO World Heritage Site, Colombia, East Pacific Ocean

Franco Banfi / Fine spotted moray eel (Gymnothorax dovii) together in a den, Malpelo Island National Park, UNESCO World Heritage Site, Colombia, East Pacific Ocean

Franco Banfi / Fine spotted moray eel (Gymnothorax dovii) together in a den, Malpelo Island National Park, UNESCO World Heritage Site, Colombia, East Pacific Ocean

Loic Poidevin / Grey heron (Ardea cinerea) feeding on European eel (Anguilla anguilla), Marais Breton, Vendée, France, January.

Loic Poidevin / Grey heron (Ardea cinerea) feeding on European eel (Anguilla anguilla), Marais Breton, Vendée, France, January.

Dave Bevan / Little grebe (Tachybaptus ruficollis) diving and catching a European eel (Anguilla anguilla) elver, Pembrokeshire, Wales, UK. October.

Dave Bevan / Grey heron (Ardea cinerea) trying to swallow a European eel (Anguilla anguilla), Pembrokeshire, Wales, UK. September.

Dave Bevan / Grey heron (Ardea cinerea) trying to swallow a European eel (Anguilla anguilla), Pembrokeshire, Wales, UK. July.

Nick Upton / European eel (Anguilla anguilla) elvers swimming in a glass holding tank, caught during their annual migration upstream for a reintroduction project, Gloucester, England, UK, March. Captive.

Nick Upton / European eel (Anguilla anguilla) elvers swimming in a glass holding tank, caught during their annual migration upstream for a reintroduction project, Gloucester, England, UK, March. Captive.

Nick Upton / European eel (Anguilla anguilla) elvers swimming in a glass holding tank, caught during their annual migration upstream for a reintroduction project, Gloucester, England, UK, March. Captive.

Franco Banfi / Jewel moray, Muraena lentiginosa, Sea of Cortez, Baja California peninsula, Mexico, East Pacific Ocean.

Franco Banfi / Scuba diver with honeycomb moray eel (Gymnothorax favagineus) at burrow, Aldabra Atoll, Natural World Heritage Site, Seychelles, Indian Ocean.

Franco Banfi / Jewel moray (Muraena lentiginosa) portrait. Sea of Cortez, Baja California, Mexico, East Pacific Ocean.

Graham Eaton / Whitemouth moray eel (Gymnothorax meleagris) swimming in shallow water, Maldives, Indian Ocean.

Philippe Clement / Scavenging Carrion crow (Corvus corone) feeding on dead European conger eel (Conger conger) washed ashore on beach along the North Sea coast, Belgium, November.

Roger Powell / Great cormorant (Phalacrocorax carbo) catching and attempting to eat a European eel (Anguilla anguilla) on the side of a tidal pool. Druidge Pools Nature Reserve, Northumberland, England, UK. August....

Nick Upton / European eel (Anguilla anguilla) elvers being released from an inflatable boat by Elliot Gough during a reintroduction project run by Severn and Wye Smokery and UK Glass Eels, Lake Llangorse, Breacon...

Nick Upton / European eel (Anguilla anguilla) elvers being released from an inflatable boat by David Blennerhassett during a reintroduction project run by Severn and Wye Smokery and UK Glass Eels, Lake Llangorse,...

Nick Upton / European eel (Anguilla anguilla) elvers being packaged at UK Glass Eels for transport to Wales for a reintroduction project, Gloucester, UK, October 2016

Nick Upton / European eel (Anguilla anguilla) elvers being packaged at UK Glass Eels for transport to Wales for a reintroduction project, Gloucester, UK, October 2016

Nick Upton / European eel (Anguilla anguilla) elvers transported in insulated boxes on an inflatable boat during a reintroduction project run by Severn and Wye Smokery and UK Glass Eels, Lake Llangorse, Breacon Be...