Haldon Pastures Trout Barrier

Solar-powered, bottom-mounted barrier in spring-fed tributary to Hororata River designed to deter upstream movement of non-native Brown Trout into critically endangered Canterbury mudfish habitat.
  • Location: Bealey Stream, New Zealand
  • Commissioned: 2019
  • Type: Waterway

Project description

The Canterbury mudfish (Neochanna burrowsius) is native to New Zealand and, as the name implies, is endemic to the Canterbury Plain south of Christchurch. It has the unique ability to absorb oxygen from air through its mouth tissues – a process known as aestivation – allowing it to survive periods of dewatering or low dissolved oxygen levels in water. Due to habitat loss, it has a conservation status of Threatened (Nationally Critical) under the New Zealand Threat Classification System.

Another threat to Canterbury mudfish populations is predation by non-native Brown Trout. The popular sportfish are known to consume mudfish in areas where they physically overlap. In Bealey Stream, a small, spring-fed tributary to the Hororata River, Environment Canterbury identified a location ideal for physically separating Brown Trout from a critical population of Canterbury mudfish. The barrier location near the confluence of the tributary with the Hororata River is on private land, but both adjacent landowners were amenable to a solution that did not inundate their land.

In 2018, Environment Canterbury engaged Smith-Root to design an electrical barrier at this location to deter upstream migration of Brown Trout into the critical habitat of the Canterbury mudfish. Smith-Root designed the 3 kW electrical barrier system, and New Zealand-based Pattle Delamore Partners contributed the site civil engineering design of the barrier system.

Notably, the barrier is 100% powered by solar electricity. A solar panel array, designed and installed by Frizzell Agricultural Electronics, charges a battery bank that provides power to the electrical barrier. The battery bank stores enough power to operate in a deficit for long periods, eliminating the need for a backup power system. The barrier system is completely separate from mains electrical power. The Haldon Pastures electrical barrier is likely the world’s largest solar-powered, permanent electrical fish barrier.

The Haldon Pastures electrical barrier was constructed in March-May 2019. Smith-Root conducted system commissioning and training of the local Environment Canterbury staff and local landowners that operate and interact with the deterrence system.

The Haldon Pastures Electric Barrier is Smith-Root’s first installation in New Zealand and in the Southern Hemisphere. To our knowledge, it is the first pulsed direct current electrical barrier installed in New Zealand and Australia.

Environment Canterbury operates the Haldon Pastures barrier as an experimental pilot development to study and research predator exclusion, population monitoring, and to experiment with innovative technologies to find new solutions while delivering biodiversity protection and sustainable land use.

News articles:


Services provided

  • Site selection
  • Barrier electrical engineering design and layout
  • Electrical barrier equipment supply and installation
  • Site commissioning
  • Staff training

Site characteristics

  • Pulsators: 1.5kVA POW
  • Pulsator Qty: 2
  • Power Output: 3kW max.
  • Water Depth: up to 1.6 m
  • Waterway Width: up to 13 m
  • Water Velocity: 0.2 to 1.2 m/sec.
  • Conductivity: up to 220 µ/cm