Monday, December 11, 2023

DOC puts bite on elusive lamprey

The prospects of an ancient fish with a stunning set of teeth are looking up thanks to a technique that detects the tiniest traces of the elusive kanakana/piharau/lamprey.

To build up knowledge of this threatened fish, environmental DNA (eDNA) research and finely tuned pheromone sampling has taken place in selected catchments around the country.

DOC Freshwater Technical Advisor, Dr Chris Kavazos says five previously unknown lamprey locations were revealed in the Taiari catchment, in Otago, as part of joint research this year with the Jobs for Nature Te Nukuroa o Matamata project team.

“Finding more evidence of lamprey is a huge win. They’re a taonga species, a source of mahinga kai for Māori, and they’re real survivors, with traits reminiscent of our earlier ancestors,” he says.

“Lamprey split off from our evolutionary chain more than 360 million years ago so, unlike virtually every other species of vertebrates, they didn’t evolve a jaw. Instead, they have a powerful ‘sucker’ full of tiny teeth. They even use their sucker mouth to climb steep waterfalls.

“However, lamprey face the same pressures as other freshwater fish, such as loss of habitat, pollution, and extreme weather events resulting from climate change.

“They used to be plentiful across the country, and there are stories of massive harvests in the past. Now they are classified as Threatened-Nationally Vulnerable.”

Finding where the secretive lamprey spawn is a big part of the battle to protect them.

Lamprey larvae give off tiny amounts of a pheromone called petromyzonol sulphate while they’re feeding. Having spent most of their adulthood at sea, lamprey follow these pheromones and are directed to streams with good habitat for breeding and for young fish to grow. 

NIWA Principal Scientist, Dr Cindy Baker has developed a method to detect the pheromone, even in miniscule amounts. 

“We can detect the chemical in the femtomolar range, which is a concentration of around 5g (one teaspoon) in 580,000 Olympic-sized swimming pools,” she says.

DOC rangers already had indications of possible spawning streams using eDNA. To get specific locations, samplers were put in streams for three weeks, where molecules of the pheromone accumulated. Cindy then extracted the pheromone and determined the amount present, which in turn identified how popular the stream is with lamprey.

DOC’s freshwater rangers around the country surveyed their local areas, covering streams in Tasman, Marlborough, West Coast, Otago, Wairarapa and Taranaki.

The results of these surveys will help to DOC to make decisions on the best ways to protect and restore lamprey populations and their habitats.

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