Underwater view of lamprey swimming turning its head back towards tail with mouth open showing teeth.

Lamprey

Introduction

Lamprey are primitive, jawless fish. They look like eels but are more closely related to sharks and rays.

New Zealand status: Native
Conservation status: Threatened - Nationally Vulnerable
Names: Lamprey have several Māori names. They are known mostly as kanakana in the South Island and piharau in the North Island.
Found in: Distributed throughout New Zealand including Chatham Islands and Stewart Island/Rakiura. This species is also widespread in the Southern Hemisphere including Australia.
Threats: Migration barriers, loss of habitat, poor water quality and some activities in streams like clearing drains.

About lamprey

Lamprey (Geotria australis) are ancient fish, which have existed for more than 360 million years. There are 38 known species worldwide but only one is found in New Zealand.

Lamprey are migratory fish, moving between fresh and saltwater to complete their lifecycle. The lamprey lifecycle is distinctly different to New Zealand’s other migratory freshwater fish. Lamprey spend most of their lives at sea and only move into freshwater to spawn and for their juvenile life stage. Other migratory freshwater fish tend to spend their juvenile life stages at sea and return to freshwater to grow into adults.

From a distance, adult lamprey could be mistaken for eels but they are easily distinguished with a closer look:

  • Eels have jaws: lamprey do not. Lamprey have a circular fleshy sucker mouth, filled with hundreds of small teeth and a rasping tongue.
  • Eels have a pair of fins near their heads: lamprey do not.
  • Lamprey have seven pairs of small holes just behind their eyes that are the openings of their external gills: eels do not.

Adult lamprey are secretive and can be very hard to spot. They often hide during the day under logs or large rocks. Lamprey use their powerful sucking mouths to climb steep waterfalls while migrating upstream.

Traditional harvest

Lamprey is a mahinga kai species for Māori and an important traditional fishery. In the past, these fish were abundant in many New Zealand rivers and were harvested using various methods.

One method was the use of lamprey weirs, known as utu piharau or pā kanakana. The weirs were common on the Whanganui River, where they consisted of large wooden barriers built out from the shore with gaps between them. Lamprey were also gathered while climbing waterfalls.

Lamprey research

Because lamprey are secretive, they are hard to find and study so relatively little is known about the species and the habitats they prefer.

In 2013 NIWA scientists found the first spawning site of a Southern Hemisphere lamprey species in a small river on Banks Peninsula in Canterbury. Three nest sites were found with eggs clumped to the underside of rocks.

Read a media release about the find.

The lamprey lifecycle takes about 9 years to complete

Adults enter freshwater and travel upstream to spawn

During winter and spring, adult lamprey move from the sea into a river and travel upstream to find habitat to lay their eggs. Lamprey mostly migrate upstream at night and when river flows are higher than normal. During the day they shelter between boulders and in debris beside stream and rivers.

Adult lamprey then spend 12–16 months in freshwater and do not feed during this time. They use fat reserves for energy and to complete the development of their reproductive organs. During this time they shrink to two thirds of their adult size and change colour from blue to a dull brownish grey. Male fish develop a large baggy pouch behind their mouths.

Lamprey can travel long distances and some have been found more than 200 km inland. Adult lamprey are very good climbers but cannot get past every instream obstacle. For example some waterfalls and dams are too high or steep or the water flow is too fast to allow the fish to pass.

Eggs are laid under boulders in streams

Lamprey spawn in spring and early summer. They choose a concealed crevice or hole with a hard surface and good water flow, laying their eggs in a cluster in this underwater ‘nest’. Both male and female fish stay in the nest for up to 7 weeks and guard the eggs from predators. The male fish seem to care for the developing larvae and help them hatch. 

Adult lamprey die a few months after spawning.

Larvae live in rivers for 3–5 years

Lamprey larvae (ammocoetes, pronounced ‘ammo-seats’) hatch in about 6 weeks and stay in the nest for another 2–3 weeks. They have no eyes and a hood over their mouths, and are a greyish brown colour.

Once the ammocoetes leave the nest, they burrow into soft sand in slow-flowing parts of the waterway. At night they partially emerge to filter-feed on algae and other microorganisms in the water.

Juvenile fish move out to sea

By January, larvae have become juvenile fish called macrophthalmia. In this life stage they have large silver eyes – their fins also enlarge and teeth develop. Macrophthalmia are a brilliant silver-blue colour with thin blue stripes along their backs.

Macrophthalmia migrate further downstream at night when the river is flowing rapidly, which accelerates their journey. By the time they reach the sea in July–August, the fish are about 80–120 mm long.

Adult fish live in the sea

Adult lamprey spend 3–4 years in the sea, growing to 450–750 mm. During this life stage, adults are a silvery blue colour.

Lamprey attach themselves to large animals like fish and whales using their sucker mouth. They feed as parasites, rasping into the host’s flesh with their sharp teeth. While at sea, lamprey can travel long distances, and have been found as far south as subantarctic waters.

Threats to lamprey and their habitat

The number of lamprey in New Zealand’s rivers is decreasing. Threats to their populations include:

  • loss of habitat when land is used more intensively
  • reduction in water quality
  • reduced water flow and loss of habitat when water is taken from rivers for irrigation
  • large instream structures like dams that prevent the fish accessing habitat upstream
  • predation from introduced freshwater fish like trout and some marine species
  • emerging parasites and diseases
  • clearing or dredging river channels that kills lamprey larvae in the sediment or damages their nests.

Lamprey reddening syndrome  

Dead and dying adult lamprey have been found in Southland rivers since 2011. These lamprey have markings like bruises over all or part of their bodies or fins. While the cause of lamprey reddening syndrome has not been confirmed, it is thought that several factors are making the fish more susceptible to a bacterial infection.

Iwi, hapū, whānau, DOC and the Ministry for Primary Industries (MPI) are researching the syndrome.

If you find dead lamprey with red markings, or fish that have died from unexplained causes, call MPI’s 24-hour hotline 0800 80 99 66 immediately.

Help protect lamprey habitat

You can help turn around the decline in lamprey populations by protecting their habitat:

  • learn about freshwater restoration work in your area by contacting local iwi and the regional council.
  • join local communities, landowners and businesses to restore streams in your area.
  • fence off waterways to keep stock out of streams.
  • plant appropriate native seedlings beside streams to enhance the habitat.
  • limit the amount of sediment and nutrients leaving your property.
  • avoid moving plants and fish between waterways.
  • ensure the culverts, weirs, dams and floodgates on your property comply with fish passage regulations.
  • dispose of chemicals properly and keep pollutants out of stormwater drains.
  • report sightings of lamprey on iNaturalist.

More information about lamprey