Monday 27 June 2016

Ngāi Tahu Research Centre seminar: earthquake recovery in Ōtautahi Christchurch watwerways

Results from our research into the effects of the Canterbury earthquakes on īnanga spawning sites in the Avon Heathcote Estuary / Ihutai catchment in Ōtautahi Christchurch. It's a story of the resilience and recovery of an iconic New Zealand species following a major disturbance. Thanks to the Ngāi Tahu Research Centre and UC Audio Visual unit the recent seminar was videoed. View the clip on U-tube here.

A good news story!

Suitable habitat for spawning sites has not only recovered in terms of the available area in the catchment, it has expanded. Because the spawning sites that are used by īnanga vary from month by month during the reproductive season, it takes a lot of measurements to come to this conclusion. Regardless of whether there are more or less adult īnanga looking to spawn during a given month, the habitat that is chosen has a defined footprint. By measuring this footprint through time we can determine how much of the catchment is suitable, and where these places are. These data have been surprisingly consistent over two years of spawning indicating that the spatial pattern we are seeing is indeed a new 'post-quake' ecology with markedly different requirements for management.

The results suggest that controls present in the pre-quake landscape that acted to constrain the availability of suitable habitat may have now been released. Regardless of whether this hypothesis is correct, the story certainly has something to teach us about managing for resilience. It throws up some interesting questions for local waterways management going forward that obviously include how to protect the new resource that nature has provided!

Some of the highlights of are our findings are:
  • the combined area of the spawning habitat in the urban waterways of Ōtautahi Christchurch is the biggest area recorded for any catchment in the South Island and one of the biggest in New Zealand.
  • post-quake, the area of suitable spawning habitat has approximately doubled in the Ōtakaro/Avon River and tripled in the Ōpawaho/Heathcote River.
  • there are a lot of eggs being produced! Over 4 months in 2015 the total was 12 million eggs. We'll soon have the 2016 figure tallied up and it is likely to be even higher.
The waterways of Ōtautahi Christchurch are a major īnanga source. Protecting īnanga sources is an essential aspect of mahinga kai and for maintaining a sustainable whitebait fishery for all New Zealanders.

Thanks to the Ngāi Tahu Research Centre and UC Audio Visual unit the recent seminar was videoed. Full clip on U-tube here.

For a copy of the presentation click the image below:

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