Sven Zacek / Otter (lutra lutra) eating Gudgeon (Gobio gobio) in Southern Estonia, January.

Richard Robinson / Smallscale dartfish (Ptereleotris microlepis) juvenile also known as Blue gudgeon at Ono-i-Lau / Ono-i-Tonga, Lau Island Group, Fiji.

Will Watson / Environment Agency Fishery and Biodiversity Officers observing Minnow trap catch from an irrigation pool, during national programme to eradicate Topmouth Gudgeon, Herefordshire, England, UK, July 2017...

Will Watson / Environment Agency Fisheries Officer releasing Minnow traps from an irrigation pool, during national programme to eradicate Topmouth Gudgeon, Herefordshire, England, UK, July 2017.

Jussi Murtosaari / Gudgeon (Gobio gobio) in aquarium, Finland, July.

Jiri Lochman / West Australian blind gudgeon (Milyeringa veritas), Cape Range National Park, Ningaloo Coast UNESCO Natural World Heritage Site, Western Australia.

Jiri Lochman / West Australian blind gudgeon (Milyeringa veritas), Cape Range National Park, Ningaloo Coast UNESCO Natural World Heritage Site, Western Australia.

MYN / Paul van Hoof / Topmouth gudgeon (Pseudorasbora parva) two adults, The Netherlands, June, Meetyourneighbours.net project

MYN / Paul van Hoof / Topmouth gudgeon (Pseudorasbora parva) adult, The Netherlands, June, Meetyourneighbours.net project

MYN / Paul van Hoof / Topmouth gudgeon (Pseudorasbora parva) adult, The Netherlands, June, Meetyourneighbours.net project

MYN / Niall Benvie / Gudgeon (Gobio gobio) Burgundy, France, April.

MYN / Paul van Hoof / Gudgeon (Gobio gobio) adult, The Netherlands, February. meetyourneighbours.net project