There was great excitement in Bath last week when reports of otter sightings on the river Avon near the city centre were referred to Avon Wildlife Trust. And only the week before we had had an excited phone call from a cyclist on the Bristol to Bath cycle path who heard what he thought was the plop of a large fish as he ate his sandwich by the river bank – only to find himself staring into the eyes of a large otter.

This is all great news for this magnificent river creature, says James Field, the Trust's otter specialist, who welcomed the recent sightings, and said: "The fact that there appear to have been a number of sightings from the same stretch of river may indicate that a female has taken up residence nearby and may have cubs. This is really exciting news!"

He explained that in the 1980s otters had been all but eradicated through a combination of water pollution and habitat loss. However, thanks to strict legal protection, improving habitats and a lot of work by conservation bodies like the wildlife Trusts, we have been seeing welcome signs in recent years that they have been starting to recover. On the river otters are top predators. They are natural explorers and will travel freely through the South West's network of rivers, streams and canals where they hunt fish and eels (along with the odd amphibian, small mammal or even duckling!). For an otter, the River Avon is a motorway, with plenty of service stations, running through the South West, and it's unthinkable that they wouldn't be using it.

However, it is still a rare privilege to actually see an otter in the flesh. Just being in the right place at the right time to catch a glimpse is a lottery with long odds. Any record of an otter is still an important piece of information that we can use to make sure that the catastrophe of the 20th century doesn't happen again. Becoming an otter spotter requires sharp eyes; they are shy, solitary, mainly nocturnal, very accomplished swimmers, and may occupy a territory including 40kms or more of watercourse. Otters use their droppings – spraint – to mark their territories and communicate with other otters.

James is always interested to hear about 'spraint' finds but he is especially keen to know if anyone finds a dead otter

He says: "It sounds macabre but, sadly, the bodies of otters killed in traffic accidents are sometimes found lying at roadsides and we can learn a huge amount from autopsies. As with spraint, the message is don't move or touch it. Just tell us where the body is, and we'll collect it."

James welcomes volunteers in the Avon and Somerset area where they can contribute to the North Somerset Otter Group – email jamesfield@avonwildlifetrust.org.uk or send sightings of otters to your local Wildlife Trust via www.wildlifetrusts.org.uk.