A new set of stamps is being issued marking the diversity of birds, mammals, insects and fish.
The 10 stamps feature the beaver, Atlantic salmon, kingfisher, beautiful demoiselle, water vole, grey wagtail, common mayfly, otter, brown trout and dipper.
Royal Mail worked with Professor of Ecology at Cardiff University Steve Ormerod on the stamp issue.
David Gold, Royal Mail’s director of external affairs and policy, said: “The UK’s rivers and riversides are beautiful to look at, but how many of us stop to think about how they came to exist in the first place?
“In these stamps we celebrate our unique natural environment with a strong focus on the rich variety of creatures that live in and alongside our rivers.”
Professor Ormerod, of Cardiff University’s Water Research Institute and School of Biosciences said “These stamps are a timely reminder of the special, highly adapted and diverse array of animals that need our streams and rivers to be in healthy condition.
“This is such a wonderful way to celebrate the UK’s rivers and to send a message – quite literally – of why they are important.”