Otters are back on the river in Pontefract after an absence of nearly 40 years.
A family of five has been filmed playing in broad daylight at a secret location.
The mammals disappeared from this area in the 1970s because of pollution but now the supreme fish hunters are making a comeback.
Nature enthusiast Francis Hickenbottom, who captured images of otters on strategically placed trail cameras, said: “I was just amazed when I saw them.
“I hadn’t realised otters had strayed back into areas they had been absent from in the past.
“In the 1970s there were none here because of chemicals used in pesticides. They disappeared from much of England apart from a few locations.
“But as water quality has improved they are spreading from their enclaves and have reoccupied suitable habitat.”
His first glimpse of an otter on an Environment Agency camera was all too brief.
So the Wakefield Naturalists’ Society member used his field craft skills to get better footage.
Mr Hickenbottom, 55, said: “I thought more carefully about the positioning of the camera and put more out. Otters are more likely to trigger a camera by coming on to land.
“So I placed a brick on a scrape of land because I know they like to mark their territories.”
The wildlife watcher caught images of foxes, mink and a bathing buzzard, but then he hit the jackpot.
Mr Hickenbottom, 55, of Fitzwilliam, said: “I saw a female adult with three youngsters. Over a period of four months I have seen them growing.
“I’ve sometimes seen a male otter. I’ve grown up in an era when you wouldn’t have dreamt of seeing otters in the Wakefield district. It’s just fantastic to be able to see them on screen.
“Plenty of people walk along the river without any idea they are there.
“I think there are more out there than people realise.
“It’s prompting me to go and look at other sites locally and see the bigger picture.
“I’m pretty certain now that if I look elsewhere I will find them.”