Freshwater crayfish Paranephrops zealandicus

Koura

Description

  • Have a hard external skeleton and two large pincers.
  • Very similar in appearance to saltwater crayfish, but do not grow anywhere near as big.

Taxonomy

  • Two species of freshwater crayfish are currently recognised:
    • Paranephrops zealandicus, found in the eastern and southern South Island, and classified as At Risk: Declining; and
    • Paranephrops planifrons, found in the North Island and northern and western South Island, and classified as Not Threatened.

Interesting Facts

  • Widespread throughout New Zealand, preferring pools and areas of slow or no flow.
  • Live in streams, lakes and ponds, and even in wetlands.
  • Shelter between stones on gravelly bottoms, but can burrow into muddy bottoms, and will burrow well down into wetlands to survive dry periods if needed.
  • Tend to stay hidden during the day, moving around mostly at night.
  • Eat a wide variety of food, mostly scavenging for invertebrates, leaves and other detritus.
  • Are a valuable mahinga kai species.

Association with Plantations

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

Threats

  • Destruction of riparian vegetation.
  • Disturbance of banks and beds of waterways.
  • Predation.
  • 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.
  • Provide adequate passage through/over artificial barriers within streams, e.g. providing mussel spat ropes for them to climb up, or using other designs (refer Buxton 1991, Jowett 1999).
  • 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 http://www.doc.govt.nz/
  • Whitmore, N., Huryn, A. D., Arbuckle, C. J., Jansma, F. 2000. Ecology and distribution of the freshwater crayfish Paranephrops zealandicus in Otago Implications for conservation. Science for Conservation 148. 42 p.
  • Buxton 1991. New Zealand’s wetlands: a management guide. Wellington, Department of Conservation.
  • Jowett I. et al. 1999. Fish passage at culverts: a review with possible solutions for New Zealand indigenous species.
  • NIWA website. http://www.niwa.cri.nz