20 Iconic River Species in the UK and Ireland
To celebrate 20 years of The Rivers Trust, Marketing and Campaigns Officer Matthew Woodard takes a closer look at 20 of the UK and Ireland’s most iconic river species.
25/11/24
Our rivers support a remarkable variety of species, from tiny insects to mighty mammals. They use our precious waterways for their homes, for navigation, to find food, and much more. To celebrate 20 years of The Rivers Trust, Marketing and Campaigns Officer Matthew Woodard takes a closer look at 20 of the UK and Ireland’s most iconic river species.
1. The Kingfisher (Alcedo atthis)
Where else would we start, other than with the kingfisher? Often only glimpsed as a brief flash of blue and orange as they dart along the water, few species conjure up the image of river quicker than the kingfisher. Did you know that to court a female, male kingfishers will approach his prospective mate with a fish in his beak? He’ll position the head facing outwards as a gift and will attempt to feed it to the female.
2. Atlantic Salmon (Salmo salar)
Atlantic Salmon are renowned for their impressive migratory journey. Beginning their lives in our freshwaters, they undertake quite the trip to reach the ocean where they then spend most of their lives before returning to their birthplace to spawn and start the cycle again. They’ve even earnt the name ‘King of the Fish’ due to an unrivalled ability to leap over obstacles (even some man-made barriers) to reach their destination.
3. Dragonflies and damselflies
These vibrant insects, known for their elongated bodies, large eyes, and veined wings are a common sight over rivers in warmer months. Skilled hunters, dragonflies and damselflies catch other insects mid-air. Even as larvae they are fierce predators, feeding on insects, newts, and small fish in the water. They can be told apart by their resting wings—dragonflies spread theirs like an airplane, while damselflies fold them back. Important to river ecosystems, they serve as indicators of water health and as a food source for birds, fish, and amphibians.
4. Water vole (Arvicola amphibius)
If you hear a soft but distinct "plop" by the river, it might be a water vole. Once common in the UK and beloved as "Ratty" from The Wind in the Willows, water voles are now the UK’s fastest declining mammal, facing habitat loss and predation by invasive American mink. Many local Rivers Trusts, including Eden Rivers Trust, are helping with habitat restoration and reintroductions to support these charming creatures.
5. European eel (Anguilla Anguilla)
Once so abundant they were used as currency, European eels have a rich history with our rivers. Starting as eggs in the Sargasso Sea, they drift 6,500 km to Europe, transforming from glass eels to elvers, then yellow eels, maturing in rivers before returning to spawn. These slender, snake-like fish now face threats from pollution and migration barriers, making them a priority for conservation efforts for our member Trusts.
6. Dipper (Cinclus cinclus)
Dippers, with their white chests and signature bobbing motion, are often seen by fast-flowing rivers. As the UK’s only aquatic songbird, they’re adapted to dive for underwater insects, boasting high haemoglobin levels for oxygen storage, a nasal flap for underwater breathing, and specialised eye muscles for clear vision below the surface. Their strong, clawed toes help them grip the riverbed even in strong waters, earning them the Welsh nickname, “bird of the torrent”.
7. Freshwater Pearl Mussel (Margaritifera margaritifera)
These little-known but mighty molluscs have an incredible life cycle that involves the larvae attaching themselves to the gills of salmonid fish and hitchhiking for up to 10 months. Once they leave their fishy taxi, the young then grow and eat algae and bacteria from the riverbed before they develop their gills at around 3-5 years old, at which point they can start filter feeding. Freshwater Pearl Mussels are remarkably long-lived with a lifespan of up to 100 years! They are a keystone species for our rivers and can help maintain water quality.
8. Daubenton’s bat (Myotis daubentoniid)
Nicknamed the ‘water bat’, these fast and agile fliers skim across the water’s surface, snatching up insects as they go. They’ll deftly catch their prey with their mouths, feet, and even tail. Speeding at up to 25 kph just centimetres above the water is a dangerous game, but Daubenton’s bats can even swim if they have a mishap.
9. Pike (Esox lucius)
A formidable predator of our rivers and lakes, pike are long, torpedo-shaped fish with powerful jaws filled with sharp teeth. With their camouflaged green and yellow body, they are a perfect ambush predator, lying motionless in vegetation before launching sudden, surprise attacks on their prey. Pike primarily feed on smaller fish, amphibians, and occasionally water birds and can take prey up to half their own body weight.
10. Brown trout (Salmo trutta)
Voted Britain’s favorite fish in 2016, the beautiful brown trout is beloved for its colors and dappled scales. Adaptable to both freshwater and saltwater, brown trout can head to sea as “sea trout” when food is scarce, returning to rivers to spawn. Interestingly, brown and sea trout are biologically the same species with sea trout simply being a brown trout that decides to head out to sea.
11. European Otter (Lutra lutra)
Beautiful, sleek, and playful, it is easy to see why the otter is a favourite wetland creature for so many people. Sitting at the top of the river food chain they will happily chow down on fish, amphibians, crustaceans, and even waterbirds. Famously elusive, you are far more likely to come across the signs of an otter than an otter itself. Whilst they remain Near Threatened on the Red List, otters are making a comeback with populations slowly increasing and every county in the UK now has a wild population.
12. Grey heron (Ardea cinerea)
The prehistoric silhouette of a grey heron standing motionless in the shallows is a familiar sight along our rivers. They wait patiently for their prey before delivering a rapid strike and spearing fish, frogs, and even small mammals with their long beak.
13. Riverflies
Mayflies, stoneflies, and caddisflies—collectively called riverflies—are known as the canaries of our rivers. Highly sensitive to water quality, their populations serve as key indicators of freshwater ecosystem health. They’re also essential food sources for many river species, making them iconic for both their ecological role and their value in tracking river health.
14. Barbel (Barbus barbus)
Hailed as the “king of the river” by anglers, the barbel is a strong and robust bottom-dwelling fish that likes fast-flowing and well-oxygenated rivers. Its name derives from the characteristic whisker-like appendages that can be seen around its mouth, which provide the fish with a keen sense of its surroundings and help it detect its favourite food of crustaceans, insect larvae, and molluscs.
15. Perch (Perca fluviatilis)
Known for their dark, tiger-like stripes and striking red fins, perch is a fish familiar to many an angler. An active predator, perch feed on insects, crayfish, and other fish, and can themselves be found living in large ponds, lakes, canals, and lowland rivers. Interestingly, perch 'talk' to each other; they can produce a series of barks, grunts, and croaks using their pneumatic duct and swim bladder.
16. White-clawed crayfish (Austropotamobius pallipes)
Recognisable by its pale namesake claws, the white-clawed crayfish is the UK’s only native crayfish. Preferring clean, fast-flowing rivers and streams, they play a crucial role in maintaining river ecosystems by feeding on detritus and small-invertebrates. Unfortunately, white-clawed crayfish are endangered, suffering dramatic declines due to the invasive non-native American signal crayfish. Many local Rivers Trusts are working hard to protect and restore our native populations.
17. Sand Martin (Riparia riparia)
Small, agile migratory birds sand martins are seen along UK rivers during spring and summer. With brown upperparts and white underparts, they are easily recognised by their graceful, darting flight as they catch insects mid-air. They nest in colonies, digging burrows into sandy riverbanks, where they lay and raise their young. These birds are among the earliest migrants to return to the UK in spring, flying thousands of miles from their wintering grounds in Africa.
18. Water shrew (Neomys fodiens)
Our largest shrew species, the water shrew inhabits the banks of our rivers, streams, and wetlands. With dense, waterproof fur and fringed hind feet for swimming, it’s well-adapted to life in the water. As voracious predators, they mainly feed on aquatic insects, however they are can take prey up to 60 times heavier than their own weight, including frogs and small fish, all because of a rather unusual characteristic — their saliva is venomous. This helps them immobilise bigger prey and makes them unique among our mammal species.
19. The European Beaver (Castor fiber)
Once extinct in the UK, beavers have been reintroduced to select areas where their dam-building skills create wetlands that benefit water quality, reduce flood risk, and support diverse habitats. As a keystone species, they play a vital role in enhancing waterways. Recognisable by their large size and distinctive tail, these herbivores feed on leaves, bark, and aquatic plants.
20. Mallard (Anas platyrhynchos)
The mallard is one of the most familiar birds on our waterways. Males are recognisable by their green heads and yellow bills, while females have mottled brown feathers for camouflage. Adaptable to both urban and rural areas, mallards feed on aquatic plants, insects, and small invertebrates, often dabbling at the water’s surface. A common but iconic bird, they’re often the first to spark people’s interest in nature.
Our rivers are home to a plethora of wonderful and fascinating species, it was hard to choose just 20! Unfortunately, many are struggling due to threats like poor water quality, barriers, and artificial changes and several of these species are central to The Rivers Trust Movement’s efforts to restore our rivers.
