Blood-sucking, snake-like fish arrive in New Brunswick waterways to spawn

It may be bad news that it's once again spawning season for the parasitic sea lamprey, meaning they're moving upriver in New Brunswick in droves. 

But the good news is that they're so focused on spawning that their digestive systems shut down. 

 "They couldn't feed if they wanted to," said Marc Gaden, the communications director for the Great Lakes Fishery Commission. 

"They have only one thing in mind once they reach that spawning phase, and that's to find a mate and to spawn successfully."

WATCH | Sea lampreys build their nest underwater near Belleisle Bay

Sometimes mistakenly called an eel, the sea lamprey is a fish with a powerful suction cup of a mouth filled with multiple circular rows of horn-shaped teeth and a tongue that burrows into the body of the host so it can liquify its tissues and feed at will. 

These lamprey spend a good part of their life at sea, attached to, and feeding off the blood of, other fish. But at this time of year, adults return to inland brooks and rivers to spawn. 

Oana Birceanu, an assistant professor at Western University in Ontario, has been studying sea lamprey for years.

"I've worked with the sea lampreys for so many years, yet I've never seen them build their nests in the wild," said Birceanu.

That's why she was fascinated by a video taken by Mike Sherwood near his Belleisle area home. It's underwater footage of several lamprey building nests in a brook in Midland. 

"It's fascinating," Birceanu said after watching the video. 

Sherwood's video show adult lamprey latching moving rocks around — some bigger than softballs.

Other parts of the video show them latched onto even bigger rocks with their powerful suction-cup mouths.