This video says about itself:
In this film we see a Brook Lamprey (sometimes also called a Lampern) in a Devon stream [in Britain].
These primitive, jawless fish feed by parasitising other fish, attaching themselves to them by their circular toothed ‘sucker’ mouths. The gills consist of 7 holes down the side of the neck behind the eyes and a nostril on top of the head. The Brook Lamprey is the smallest of the three species found in Britain (these were about 6 inches long) and unlike its larger relatives the river and sea lampreys it spends its whole life in freshwater.
Although these creatures are not always fondly referred to, we found the Lampreys to be very attractive fish. They are a fetching olive green colour with a silvery underside and their faces are cute and almost muppet-like.
The Lamprey is said to be secretive and rarely observed so this intimate sighting at very close quarters was a treat indeed! And the creatures seemed utterly unaware of our presence.
After the event we managed to find out the cause of the curious behaviour witnessed here. The film was taken in early April and shows the fish spawning. A female (or possibly two) is making a ‘nest’ (a small depression in the gravel) by moving the stones and gravel with her sucker. In this example they are spawning in a group. The film shows three but there were actually at least four, probably two of each gender.
By Jon Land:
Rare fish returns to UK waters ‘in large numbers’
One of Britain’s rarest fish is returning in large numbers, the Environment Agency said today.
Scientists have witnessed a massive resurgence in the sea lamprey population in the River Tamar and have recorded five times more fish than the seasonal average.
The Environment Agency (EA) picked up the increase in lamprey numbers while recording migrating salmon at Gunnislake, Cornwall, as they swim upstream.
The EA welcomed the resurgence as it indicates a healthy river environment and said the metre-long sea lamprey is a primitive marine species that comes into rivers to spawn.
The eel-like fish has a jawless mouth and is boneless with a skeleton made of flexible cartilage.
Spokesman for the EA, Paul Elsmere, said: “The sea lamprey is something of an evolutionary throwback, but it is an important indicator species.
“This year more than 500 have passed through our fish counter at Gunnislake which is excellent news as it shows water quality in the Tamar is high.”
The EA said the sea lamprey are thought to be more sensitive to pollution than salmon so their presence on any river system is to be encouraged.
For centuries the fish was considered a delicacy in Europe and King Henry I is said to have died from a “surfeit of lamprey”.
In Finland, hot-grilled lamprey it still a favourite dish although there is no commercial fishery for sea lamprey in the UK and little is known of its behaviour at sea.
It feeds by attaching itself to other fish using its sucker mouth. Once attached it uses its sharp tongue to rasp a hole in the side of the fish before feeding on its host’s blood.
The lamprey later detaches itself and swims off in search of its next meal. The EA said it rarely kills other fish.
See also here.
River lampreys: here.