Kakahi, our Freshwater Taonga

28 June, 2018

The ecology division have been battling the elements… Recent weather events are illustrating how vunerable our water systems are to modifed human activities on the land.

The Kaipara District and its associated catchments is home to the little known freshwater mussel -kakahi/kaeo (Echyridella spp.). Kakahi are widespread in New Zealand currently consisting of three species, found from fast-flowing streams to lakes. Kakahi populations have been decreasing, impacted by destruction of their habitat. Koaro (Galaxias brevipinnis), which are fish hosts for parasitic larval stage of the freshwater mussel are also impacted by the destruction of  suitable stream habitat (NIWA, Kakahi, 2018). The two freshwater mussel species recorded in the district are (Echyridella aucklandica) listed as ‘Threatened, Nationally Vulnerable’ and (Echyridella menziesii) ‘At risk’  (Williams, et al., 2017).

This shell found within the Hakaru Stream belongs to (Echyridella aucklandica), which would have been transported downstream by the recent flood events. It is anticipated that there is also (Echyridella menziesii) upstream as the two species generally co-exist. Kahai are important indicators of freshwater quality as they filter feed food particles. Being filter feeders the kahai are susceptible to a range of pollutants including agricultural activities. Kakahi are naturally predated by fish, birds and koura but also by rats (Williams, et al., 2017).

Whole catchment management approaches are a key way to improve the habitat and potential habitat of these species via pest animal and plant eradication coupled with eco sourced riparian planting.

Further reading please see:-

Williams, E., Crow, S., Murchie, A., Tipa, G., Egan, E., Kitson, J., . . . Fenwick, M. (2017). Understanding Taonga Freshwater Fish Populations in Aotearoa-New Zealand. National Institute of Water & Atmospheric Research Limited, Wellington. Retrieved June 29, 2018

NIWA. (2018). Kakahi. Retrieved June 26, 2018, from NIWA: https://www.niwa.co.nz/our-science/freshwater/tools/kaitiaki_tools/species/kakahi

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