A young fisherman and his granddad caught a rare ancient and mysterious native fish during a 13-hour stint on the Ashley River recently.

Archie Day, aged 10, and Graham Day, caught the kanakana (lamprey), a silver-blue coloured fish, in their whitebait net. 

After photographing it they lowered it back into the river, having read about a previous sighting in a recent North Canterbury News article.

The earlier sighting was made by Environment Canterbury’s environment monitoring technician, Anna Casey in the Waimakariri River who described it as as “career highlight”.

Archie’s dad, Brett, says the catch came at 4.30pm —  5pm, during a long day on the river, starting at 6am. 

Archie is a mad keen fisherman, hunter and ocean fisherman.

Prized catch . . . Archie Day, and grand dad Graham (rear), after catching a kanakana (lamprey), a rare native fish, in the Ashley River recently. They returned it to the water. Photo: Supplied

"He is out there doing it,’’ he says.

Seeing the blue lamprey in the net was a highlight of the day, and ECan had been informed of the catch.

Despite often being mistaken for eels, kanakana are more closely related ot sharks and stingrays.

With ther eel-like bodies, suction-cup mouths, and ancient appearance, they are one of New Zealand’s most unusual native fish.

Once common in rivers across the country and an important taonga and mahinga kai species, kanakana are now classified as Threatened — Nationally vulnerable.

They spend most of their lives at sea, where their silver-blue colouring helps camouflage them in the open ocean.

When it is time to breed they return to freshwater rivers and streams to spawn.

Spotting one still blue is considered a rare glimpse of the very beginning of that remarkable migration.