|Sea lamprey returns to UK 'in large numbers'|
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.