Kākahi in the Ōtākaro-Avon River

Snorkellers took to the Ōtākaro-Avon River to count the number of kākahi, an at-risk, culturally significant native freshwater mussel. Over 2,200 kākahi were identified in the survey area, between Fitzgerald Avenue and Anzac Drive. Several identified populations are regionally significant and confirm how valuable the lower Ōtākaro-Avon River is as a habitat for kākahi populations.

Like saltwater mussels, kākahi have hinged shells; however, they do not attach themselves to surfaces. Instead, they wedge themselves into the beds of waterways.

They are particularly at-risk in urban waterways such as the Ōtākaro-Avon due to waterway pollution, waterway modification, and activities like dredging – the removal of sediment or weeds from waterways. Understanding and protecting kākahi is important as they are a taonga species and play a role in cleaning our freshwater.

The Christchurch City Council, CWP partner and facilitating body, commissioned a kākahi survey in the lower reaches of the Ōtākaro-Avon River. As there are a multitude of projects planned for the Ōtākaro-Avon River Corridor (OARC), understanding the distribution and abundance of these taonga is crucial.

Snorkellers from Instream Consulting entered the waterway at 57 different sites to identify and count kākahi. Notes about their location, habitat and size were also made.

Kākahi can be difficult to spot during surveys as they are often partially buried, so the team used both visual and tactile techniques. Most kākahi were located in open areas of riverbed sediment and near aquatic plants. Some were also observed amongst small stones and on manmade structures like bridges.

The survey highlighted significant populations of kākahi in the lower Ōtākaro-Avon between the Fitzgerald Avenue and Anzac Drive bridges. The findings and recommendations made will assist the Christchurch City Council to protect kākahi populations while work is underway in the OARC.

Download the full report  [PDF, 2.7 MB]