After two years of groundwork, NIWA scientists have finally unlocked the mystery of the elusive lamprey breeding grounds.
Dr Cindy Baker, a freshwater scientist based in Hamilton, and Tyler Buchinger, a visiting lamprey scientist from Michigan State University were on a field expedition in the Okuti River Catchment on Banks Peninsula recently, tracking lamprey that the NIWA team had electronically tagged a year earlier in a bid to discover where they spawn.
The team uncovered three nesting sites in the river made by monogamous pairs of lamprey – the first discovery of its kind in the Southern Hemisphere.
Lamprey and hagfish are the only living jawless vertebrates, over 360 million years old. In New Zealand, lamprey (also known as kanakana and piharau) are an important taonga species for Maori, once prolific, although now believed to be in decline and rarely seen – especially in the North Island.
Northern Hemisphere species of lamprey are known to spawn their eggs in the gravel of riverbeds, but the Southern Hemisphere species is quite 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," Dr Baker said.
Lamprey populations are strongest in the South Island but little is known about their biology, where they spawn, what cues are used to select spawning streams and their preferred habitat. Dr Baker says she hopes that now they have discovered the spawning nests, the information learned can be used to help restore lamprey populations and habitats.
What is known about lamprey is that the young 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 fish before returning as adults to freshwater to spawn. They will spend up to 16 months in freshwater before spawning occurs. Once spawning is complete they die.
Scientists are also working to discover the chemical compounds or pheromones migratory adult lamprey use to select spawning streams, as well as that secreted by the male adult lamprey to attract females to the nest site, with the aim of using the chemical cues to attract lamprey back to areas where they have declined.
Dr Baker says the Southern Hemisphere species have morphological differences from the Northern Hemisphere species and it may be possible that the female lamprey is also secreting a pheromone.
"That's the next step of our research."
