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Echyridella menziesii
Conservation status
	; Declining (NZ TCS)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Unionida
Family:	Unionidae
Genus:	Echyridella
Species:	E. menziesii
Binomial name
	Echyridella menziesii; (Gray, 1843)
Synonyms
	Diplodon menziesii (Gray, 1843) ; Diplodon menziesii acuta Suter, 1907 ; Hyridella menziesii Gray, 1843 ; Unio waikarensis Colenso, 1845 ; Unis depauperata Hutton, 1883 ;

Echyridella menziesii, the New Zealand freshwater mussel, also known by its Māori names kākahi, kāeo, and torewai,^{[citation needed]} is a species of freshwater mussel endemic to New Zealand. E. menziesii is an aquatic bivalve mollusc in the family Unionidae, the river mussels.

They were an important food source for the Māori,^[4] but like many freshwater mussels worldwide, are now endangered by pollution and eutrophication of rivers, and the introduction of new species of fish^[5] leading to actions via the Treaty of Waitangi claims process.^[6]

It is one of three species of native freshwater mussels identified in New Zealand, the others being Echyridella aucklandica and Echyridella onekaka.

Taxonomy

The species was first described by John Edward Gray in 1843,^[2] who named the species after Archibald Menzies, the surgeon of HMS Discovery.^[7]

Distribution

Formerly common in lakes, rivers and streams in New Zealand.^[8]

Ecology

Life cycle

Its reproductive cycle is typical of other freshwater mussels, requiring a host fish on which its larvae (glochidia) parasitise and metamorphose into juvenile mussels – most commonly the kōaro (Galaxias brevipinnis) and Gobiomorphus cotidianus.^[9]^[10]^[7]

Feeding

While Echyridella menziesii are parasitic as larvae, juveniles feed by grabbing food using their foot. Adult Echyridella menziesii are filter feeders, feeding on phytoplankton, animal matter and bacteria. A single mussel is able to filter a litre of water every hour.^[7]

Threats

The destruction or modification of the habitat of the New Zealand freshwater mussel is likely to be a factor in the decline of its population. This modification or destruction of freshwater habitat is also likely to be a factor in the decline in numbers of the mussel's host fish, the kōaro.^[11]

History

Kākahi has been a traditional food for Māori since the Archaic period of Māori history, and can be found in many early middens. The presence of kākahi around the central North Island lakes may have been a major reason for many central North Island iwi to settle around the lakes. The mussels were harvested by using a rou kākahi, a tool used to dredge mussel beds. Kākahi shells were traditionally used as cutting implements, and strings of shells were used as a way to scare rats away from kūmara (sweet potato) plantations.^[7]

Conservation status and efforts

In May 2014 the Department of Conservation classified the New Zealand freshwater mussel under the New Zealand Threat Classification System as "At risk" and "declining".^[1]

References

^ ^a ^b Grainger, Natasha; Collier, Kevin; Hitchmough, Rod; Harding, Jon; Smith, Brian; Sutherland, Darin (May 2014). Conservation status of New Zealand freshwater invertebrates, 2013 (PDF). Wellington, New Zealand: Department of Conservation. p. 15. ISBN 9780478150155. Retrieved 24 June 2016.
^ ^a ^b "Echyridella menziesii (Gray, 1843)". www.NZOR.org.nz. New Zealand Organisms Register. Retrieved 24 June 2016.
^ "Echyridella menziesii (Gray, 1843)". WoRMS. World Register of Marine Species. Retrieved 24 June 2016.
^ "Resource Management Issues of Significance to Iwi"
^ Butterworth, Joseph (2008). Lake Rotokakahi: The kakahi (Hyridella menziesi) in a general framework of lake health (MSc thesis). The University of Waikato.
^ "Muriwhenua Fisheries Claim / SOE Claim" Archived 27 May 2010 at the Wayback Machine, Waitangi Tribunal
^ ^a ^b ^c ^d Vennell, Robert (5 October 2022). Secrets of the Sea: The Story of New Zealand's Native Sea Creatures. HarperCollins Publishers. pp. 38–43. ISBN 978-1-77554-179-0. LCCN 2021388548. Wikidata Q114871191.
^ "Freshwater mussel". Te Ara - the Encyclopedia of New Zealand.
^ McDowall, Bob (2002). "Decline of the kakahi - identifying cause and effect". Water & Atmosphere. 10 (4): 8–9. Retrieved 12 January 2019.
^ "Kākāhi - the mysterious freshwater mussel", Greater Wellington Regional Council.
^ "Kākahi". NIWA. National Institute of Water and Atmosphere. Retrieved 24 June 2016.