How to identify freshwater wildlife

A spring riverside stroll reveals fresh arrivals and newly emerged animals. Use our handy guide to look out for 11 species and the telltale signs left by a twelfth – the otter. 

Common sandpiper
All illustrations by Dan Cole/The Art Agency


1 Common sandpiper Actitis hypoleucos

18–20cm. Summer visitor; arrives in March–April. Nests on fast-flowing rivers, mainly in north and west.



2. Sand martin Riparia riparia

12–13cm. Summer visitor; arrives in March. Told from house martin by chest band. Nests in sandy banks.



3. Goosander Mergus merganser

58–68cm. Fish-eating ‘sawbill’ duck with long serrated bill. Nests on fast-
flowing rivers in north and west.



4. Otter prints & spraint Lutra lutra

Prints: five toes (not four as in foxes or dogs) above large pad mark. Spraint: smells sweet, not fishy like mink.



5. Bullhead/Miller’s thumb Cottus gobio

Up to 8cm. Fat, flat-topped head; large pectoral fins at sides. Hides near stones in well-oxgenated rivers.



6. Minnow Phoxinus phoxinus

Up to 5cm. Slim, with dark mottling along flanks. In shallows, often in large shoals when spawning.



7. Water moss Fontinalis antipyretica

Long stems up to 20cm in length; UK’s largest aquatic moss. Attaches to stones or submerged tree roots.



8. Opposite-leaved golden saxifrage Chrysosplenium oppositifolium

Creeping plant with tiny gold flowers. On damp riverbanks, often in woods.



9. Butterbur Petasites fragrans

Pink flower spikes appear March–May, before huge round leaves unfurl. On damp riverbanks, often in woods.



10. Alderfly Sialis lutaria

10–15mm. Brown, strongly veined wings. A sluggish fly with weak flight; often rests on waterside vegetation.



11. Large dark olive Baetis rhodani

Body: 8–12mm; tails: up to 18mm. On wing January–April. Abdomen grey (male) or red-brown (female).



12. River skater Aquarius najas

13–17mm; larger than common pond skater. Floats on surface film of rivers, mainly in north and west.

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