The removal of silt has helped encourage the return of otters
Otters and water voles are returning to Oxfordshire's canals to make their homes - because of the increased cleanliness of its waterways.
British Waterway's annual wildlife survey has shown a rise in the number of dragonflies on the UK's canals.
Local ecologist James Clifton said dragonflies were one of the best indicators of good water quality.
The Oxford Canal between the city and Thrupp is a particularly "good stronghold" for water voles, he said.
Ecologists are working hard to improve the environmental and ecological conditions for previously endangered animals and remove problems like silt, he said.
"Canals and waterways provide a vital role in improving wildlife conditions in towns and cities, particularly for species like otters," he said.
"We are also trying to discourage mink. Better waterways brings the otters back and mink hate living next to otters so they move on - otters come back and so the water voles come back."