Ripples of excitement are spreading through Europe's rivers and wetlands.

A generation ago, otter watching was a wildlife highlight restricted to remote coastal areas – otter populations had been decimated over the previous century by pesticide poisoning and habitat disturbance. Now we are seeing the positive effect of determined conservation efforts over recent decades. As our waterways improve, otters are returning and spreading throughout their former habitats.

One of the UK's leading natural history photographers, Laurie Campbell got to know otters while working in Scotland's Highlands and Islands, but he had never seen these elusive predators on his home beat. Then, in the early 1990s, he was delighted to find otters back on the Tweed and its tributaries, a river system he has lived close to for most of his life. The discovery launched him on a quest to create a photographic account of their lives on his home river.

More than two decades later, otter numbers continue to increase, and new generations of otters have become more confident around people, sometimes appearing in broad daylight and in town centres. Laurie continues his long-standing study, still photographing the otters through the changing seasons – always with an eye on the bigger picture of the river itself and the plants and animals that share the otters' habitat.

Wildlife journalist and writer Anna Levin accompanies Laurie to the riverbank and learns of his working philosophy and fieldcraft. Together they weave a wealth of information into the stories that the pictures tell. While extracts from Anna's notebooks offer a vivid glimpse of the photographer at work and the otters that enchant them both.