New Zealand and US scientists have discovered the first southern hemisphere breeding ground of a lamprey species.
Electronically-tagged lamprey have been tracked to three spawning sites in the Okuti River on Banks Peninsula, where the eggs were found under boulders.
Northern hemisphere lamprey species spawn their eggs in riverbed gravel, but the southern hemisphere species is unique in pairing up underneath large boulders and secreting their eggs in an adhesive clump to the underside of the rock.
"That's why spawning lamprey haven't been spotted before," says New Zealand fresh water scientist Cindy Baker.
She and Tyler Buchinger, a visiting lamprey scientist from Michigan State University, discovered the spawning site after tagging the fish a year earlier.
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Primitive lamprey and hagfish are the only living jawless vertebrates, over 360 million years old.
Dr Baker hopes that after discovering the spawning nests, information can be used to help restore threatened lamprey populations and habitats.
Lamprey larvae spend several years living in the sediment of stream beds before undergoing metamorphosis and heading out to sea.
They feed by burrowing into the flesh of other mammals before returning as adults to freshwater to spawn. They will spend up to 16 months in freshwater before spawning.
After spawning they die.
Scientists are also researching the chemical compounds migratory adult lamprey use to select spawning streams, as well as that secreted by the male adult lamprey to attract females.
The chemicals, or pheromones, could attract lamprey back to areas where they have declined.
