Michel Roggo / Watermilfoil (Myriophyllum spicatum) with some stems supporting clusters of Zebra mussel (Dreissena polymorpha) Lake Neuchatel, Switzerland. Highly commended in the Plants category of the Wildlife Pho...

Jack Perks / Common carp (Cyprinus carpio) swimming in a river, feeding on Zebra mussels (Dreissena polymorpha). The animal swims out of the frame. London, UK.

Alex Mustard / A group of highly invasive Zebra mussels (Dreissena polymorpha) growing on an underwater structure, Whittlesea, Cambridgeshire, UK.

Chris Shields / Illustration of Zebra mussel (Dreissena polymorpha)

Michel Roggo / Wels catfish (Silurus glanis), on the bed of the Aare river, with Zebra mussel (Dreissena polymorpha) Brugg, Canton of Berne, Switzerland. October. Photographed for The Freshwater Project.

Michel Roggo / Watermilfoil (Myriophyllum spicatum) with Zebra mussel (Dreissena polymorpha) attached to stems. Lake Neuchatel, close to Boudry, Canton of Neuchatel, Switzerland. October. Photographed for The Freshw...