Freshwater mussel Echyridella spp.


  • Oval-shapped shell, hinged in centre.
  • Shell is dark coloured with gold tinges.
  • Occasionally an orange or other coloured encrustation on the shell may be present, as a result of a build up of minerals from surrounding waters.


There are currently three freshwater mussels in the genus Echyridella which are listed as Threatened or At Risk:

  • Echyridella aucklandica, found in the North Island and in the South Island from Lake Manapouri to Lake Hauroko, and classified as Threatened: Nationally Vulnerable;
  • Echyridella menziesii, found throughout New Zealand, and classified as At Risk: Declining; and
  • Echyridella onekaka, found in north west Nelson, and classified as At Risk: Naturally Uncommon.

Interesting Facts

  • Kākahi are unique to New Zealand.
  • Widespread throughout New Zealand, in habitats ranging from small, fast-flowing streams to rivers and lakes.
  • Are a valuable mahinga kai species.
  • Have a complex lifecyle - their parasitic larvae attach to a host fish (most commonly koaro) and once carried upstream they drop off into soft, sandy sediments of rivers and lakes.
  • Are long-lived, up to 50 years or more.
  • Filter feed, in the same way that other shellfish do.

Association with Plantations

  • Can occur in plantation forestry areas.
  • Plantation streams and lakes often have relatively high populations of indigenous species.


  • Destruction of riparian vegetation.
  • Disturbance of banks and beds of waterways.
  • Harvesting.
  • Habitat destruction from:
    • Modification of riparian margins.
    • Introduction of aquatic weeds.
    • Siltation.
    • Eutrophication (high nutrients).
    • Erosion of banks through grazing by livestock, goats and deer.
    • Artificial barriers to upstream migration (e.g. culverts, fords with large lips creating a drop off).
    • Depleted flows caused by water abstraction.

Management Options and Methods

  • Maintain corridors of riparian vegetation along banks. Corridors should be as extensive as possible (refer to Buxton 1991).
  • If possible, expand width of riparian zones during later rotation planting.
  • Exclude livestock from riparian areas.
  • Control deer and goats that could enter riparian areas.
  • Comply with best forest operational management practices to avoid damage to riparian areas.
  • Manage or prevent water abstraction from critical habitat areas.
  • Regulate or prevent harvesting of threatened species.
  • Prevent introductions of exotic fish.
  • Prevent introductions of aquatic weeds. Educate local users of weed threats and how to prevent spread.

Monitoring Options

  • Undertake surveys to identify presences of species and habitats.
  • Consider repeating surveys every few years to ascertain whether key species are still present.
  • Liaise with DOC about survey and monitoring methods.
  • Report findings to DOC.
  • Periodic checks of banks to ensure compliance with best forest operational management practices, pest and weed levels and siltation.

Further Information and Support

  • DOC – advice for management, survey, and monitoring. Website
  • James, M. 1987. Ecology of the freshwater mussel, Hyridella menziesi (Gray) in a small oligotrophic lake. Arch. Hydrobiol. 108: 337-348.
  • NIWA website.