Franco Banfi,Franco Banfi / Piraputanga (Brycon hilarii) in the main spring Aquario Natural that goes in the Rio Baia Bonita, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Piraputanga (Brycon hilarii) reflecting on the water surface, Aquirio Natural, Bonito, Mato Grosso do Sul, Brazil

Linda Pitkin / 2020VISION / White clawed crayfish (Austropotamobius pallipes) underwater on riverbed, showing defensive posture, River Leith, Cumbria, England, UK, September 2012. Did you know? White clawed crayfish can live fo...

Linda Pitkin / 2020VISION / White clawed crayfish (Austropotamobius pallipes) underwater on riverbed, River Leith, Cumbria, England, UK, September 2012.

Linda Pitkin / 2020VISION / Brown trout (Salmo trutta) fry on river bed, Cumbria, England, UK, September.

Michel Roggo / Grayling (Thymallus thymallus) on spawning ground. Lac de Fenetre, alpine lake, 2456 m above sea level, Canton of Valais, Switzerland, June.

Michel Roggo / Sockeye / Red Salmon (Oncorhynchus nerka) on spawning migration; males surrounding a female. Adams River, British Columbia, Canada, October.

Michel Roggo / Sockeye / Red Salmon (Oncorhynchus nerka) on spawning migration. Adams River, British Columbia, Canada, October.

Laurie Campbell / Brown trout (Salmo trutta) resting on river bed near the Aigas Field Studies Centre, Inverness-shire, Scotland, July

Graham Eaton / Underwater landscape within a mountain stream, showing water turbulence, Snowdonia NP, Gwynedd, Wales, UK, December

Graham Eaton / Underwater view of River Glaslyn rapids, Snowdonia NP, Gwynedd, Wales, UK, April

Todd Mintz / Sockeye salmon (Oncorhynchus nerka) split level view of salmon on river bed, annual spawning run, Adams River, British Columbia, Canada, October