man said they could be lampreys spawning.
No interactions present.
The blunt head, downturned mouth / sucker and fin configuration would perhaps suggest a Lamprey.
I've assumed that those are stones and pebbles in the stream and not boulders, hence the size would suggest a Brook Lamprey. They breed / spawn in small numbers and die shortly afterwards.
Chris Brooks - www.dragonfly-images.co.uk
My Flickr site - www.flickr.com/photos/ceb1298
Lat/Lng: 54.271, -2.758
OS grid ref: SD507864
under duel carriageway bridge..