Tracking down elusive lamprey

Date:  07 November 2023

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.

“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.”

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.

Background information

Te Nukuroa o Matamata

Te Nukuroa o Matamata is a Jobs for Nature project delivered by Te Rūnaka ō Ōtakou. The project focuses on restoring the Taiari catchment through improving water quality and seeking to reverse the negative effects of drainage, development and adverse land use practices. Biodiversity enhancement is happening in the catchment through a range of wetland, river and riparian habitat restoration, including matauranga Māori to empower kaitiakitanga.

Lamprey

Lamprey are born upriver and spend the next three to four years in our waterways as juveniles. When they turn into adults, they travel down to the ocean where they hitch a ride on larger fish or whales and lead a parasitic lifestyle for several years. They then swim back upstream and respond to pheromone cues released by lamprey larvae to ensure they return to waterways with the proper nesting habitat they require. Once paired with a mate, they will spawn and guard the eggs from predators. The adults die a few months after spawning.

Lamprey are secretive and can be very hard to spot. They often hide during the day under logs or large rocks, or burrow into streambeds, with juveniles venturing out at night to feed, and adults moving around also mostly at night (adults don’t feed at all once they return to freshwater after their marine phase).

Lamprey have several Māori names. They’re known mostly as kanakana in the South Island and piharau in the North Island.

Read more on the Conservation blog: Finding the fish that swam with dinosaurs

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