Lamprey

Lamprey: Ancient Survivors of New Zealand Waters
Lamprey (Geotria australis), commonly known as New Zealand lamprey or piharau, are eel-like fish native to the freshwater rivers and coastal waters of New Zealand. These ancient creatures are characterised by their long, slender bodies, lack of paired fins, and distinctive circular, suction-cup-like mouth filled with rows of sharp, rasping teeth.
Physical Characteristics
Adult lamprey can reach lengths of up to 60 centimetres and display a striking blue-grey colouration with silvery undertones. Their unique physical features distinguish them from other eel-like species found in New Zealand waters.
Lamprey vary in colour depending on their stage of life and environmental conditions. Larvae are typically light brown or grey, blending seamlessly with the sediment in which they burrow. As they mature into juveniles and adults, their colouration shifts to blue-grey with a silvery sheen, aiding their camouflage in both freshwater and marine environments.
Key Features
Circular, suction-cup-like mouth
Rows of sharp, rasping teeth
No paired fins
Blue-grey with silvery undertones
Up to 60cm in length
The Remarkable Life Cycle
Lamprey undergo one of nature's most fascinating transformations, moving through distinct life stages across freshwater and marine environments. Their complex life cycle demonstrates remarkable adaptability and survival strategies.
Eggs & Larvae
Eggs laid in freshwater streams hatch into ammocoetes, which burrow into sediment and filter-feed on microorganisms for several years.
Transformation
After a lengthy larval stage, they undergo metamorphosis, developing eyes and characteristic sucking mouthparts.
Marine Phase
Juveniles migrate to the sea, spending years parasitising larger fish by feeding on their blood and bodily fluids.
Return to Spawn
Adult lamprey return to freshwater to spawn, completing their remarkable life cycle.
Feeding Habits & Ecological Role
Specialised Parasitic Feeding
Lamprey have a diverse diet that includes the blood and tissue of various fish species. Their parasitic feeding habits are highly specialised and enable them to exploit a range of host species, which supports their survival in diverse marine environments.
In New Zealand, lamprey play a vital role in the freshwater and marine ecosystems. As both prey and predator, they are integral to the food web, providing a food source for larger fish and marine mammals whilst also controlling populations of their host species.
Ecosystem Indicator: Their presence indicates healthy, functioning rivers and marine ecosystems, making them valuable biological indicators of environmental quality.
Where Lamprey Thrive in New Zealand
Lamprey are found in various regions of New Zealand, particularly in rivers and streams that flow into coastal waters. They thrive in clear, well-oxygenated freshwater environments with suitable sediment for larval burrowing and clean, unpolluted waters for spawning.
Waikato River
One of New Zealand's longest rivers, providing essential spawning grounds and migratory routes for lamprey populations.
Whanganui River
A vital habitat offering the clean, well-oxygenated waters necessary for lamprey reproduction and development.
South Island Streams
Various streams provide the essential conditions for their complex life cycle, including safe spawning grounds.
Environmental Threats & Challenges
Lamprey face several significant challenges that impact their populations and conservation status. These threats span from physical barriers to chemical pollution, all of which compromise their ability to complete their complex life cycle.
Habitat Degradation
Changes in water quality due to agricultural runoff, industrial pollution, and urban development adversely affect their habitats and reproductive success.
Migration Barriers
Dams and weirs obstruct their migratory routes, preventing them from reaching essential spawning grounds and completing their life cycle.
Water Pollution
Pollutants from various sources degrade water quality, impacting both larval development and adult spawning success.
Climate Change
Altered water temperatures and flow patterns impact their migration and spawning behaviours, posing long-term survival challenges.
Climate Change: Temperature & Flow Impacts
Climate change significantly impacts lamprey spawning grounds through various mechanisms. Lampreys are highly sensitive to water temperature, which regulates their migration and spawning behaviour. Rising temperatures can cause several disruptions to their delicate life cycle.
Altered Migration Timing
Elevated temperatures can lead to premature or delayed migrations, resulting in a mismatch between spawning events and optimal environmental conditions for egg and larval development.
Accelerated Development
Higher water temperatures can accelerate development rates of lamprey eggs and larvae, increasing mortality if larvae are not adequately prepared for subsequent life stages.
Drought Impacts
Increased frequency of droughts reduces water levels in rivers and streams, exposing lamprey eggs and larvae to desiccation and predation. Low water levels also concentrate pollutants, further degrading water quality.
Flood Events
Increased intensity and frequency of floods can wash away eggs and larvae, destroy spawning nests, and disrupt the deposition of fine sediments required for larval burrowing.
Habitat Degradation & Ocean Conditions
1
Reduced Oxygen Levels
Warmer water holds less dissolved oxygen, which is crucial for the development of lamprey eggs and larvae. Low oxygen levels can lead to increased mortality rates among developing lampreys.
2
Increased Sedimentation
Changes in vegetation and increased runoff from more frequent and intense rainfall lead to sedimentation in spawning streams. This sedimentation can smother eggs and reduce the quality of burrowing habitats for larvae.
3
Ocean Acidification
Increased CO₂ levels lead to ocean acidification, which can affect the sensory and neurological functions of marine organisms, including lampreys, potentially reducing their survival rates during the marine phase.
4
Altered Prey Distribution
Changes in ocean temperatures and currents affect the distribution and abundance of prey species, impacting the growth and survival of juvenile lampreys before they return to freshwater to spawn.
Range Shifts & Adaptation Challenges
Forced Migration to New Habitats
As water temperatures rise, the suitable habitats for lamprey spawning may shift geographically. Lampreys might be forced to migrate to higher-altitude streams or rivers with cooler temperatures.
This migration increases energy expenditure and the risks associated with moving to new areas. Furthermore, this shift can lead to increased competition for resources in these new habitats, as lampreys and other species vie for limited space and food.
Such range shifts can disrupt the ecological balance and pose additional challenges to lamprey populations already stressed by climate change.
60%
Habitat Loss
Potential reduction in suitable spawning grounds due to temperature changes
35%
Increased Competition
Rise in resource competition as species shift to cooler habitats
45%
Energy Expenditure
Additional energy required for migration to higher-altitude streams
Conservation: Protecting an Ancient Species
Lamprey (Geotria australis) are an ancient and fascinating species, with a life cycle and ecological role that underscore the importance of preserving their habitats and ensuring the sustainability of their populations through effective conservation measures.
01
Climate Change Mitigation
Implement strategies to reduce greenhouse gas emissions and mitigate the impacts of climate change on aquatic ecosystems.
02
Habitat Protection & Restoration
Protect and restore critical habitats, including spawning grounds and migratory routes, ensuring clean, well-oxygenated waters.
03
Water Quality Monitoring
Establish comprehensive monitoring programmes to track water quality, temperature, and flow patterns in lamprey habitats.
04
River Flow Management
Manage river flows to maintain suitable conditions for lamprey spawning and development, including removal of migration barriers.
Climate change poses significant challenges to the sustainability of lamprey populations. Effective conservation strategies must consider these multifaceted impacts to protect and sustain lamprey populations for future generations.