Whitebait habitat case study

Case study in the biogeographic impacts of disaster events

A component of the Resilient Shorelines study set out to determine if the earthquake effects had altered the location and pattern of sites utilised by īnanga (Galaxias maculatus) for spawning, which are typically restricted to very specific locations in upper estuarine areas near the freshwater-saltwater interface. As such, īnanga spawning sites are potentially a very good indicator of change, and conversely, īnanga may be especially vulnerable to hydrological alterations caused by disturbance events.

And the answer is - yes, there were some major changes!
Read the report on TVNZ ONE News 

In general, findings from our very first year of research provided strong support for our major hypotheses around habitat shifts and new vulnerabilities - but also indicated there was a lot more work to be done to better understand the causes and consequences of change.

Follow these links to read more about the habitat mapping work and fascinating results!

Unexpected findings - a bonus effect?

Results from 2015 for the Ōpawaho/Heathcote River showing
maximum area of occupancy recorded over four months
for the 32 sites at which spawning was detected
A surprising result from our early work was the discovery that spawning habitat had expanded following the Canterbury earthquakes, and was more extensive than ever previously recorded (Orchard & Hickford, 2016). Further studies in 2016 found even greater areas of spawning habitat (Orchard et al., 2018). The total area involved was nearly 2x the next largest area of spawning habitat recorded in any catchment in New Zealand (based on records in the National Īnanga Spawning Database). 

Despite this apparent bonus, many of the locations involved were exposed to threats that resulted in high egg mortality. This is not surprising given that many of these area were previous known to provide spawning grounds. 

Looking forward, it is important to protect those areas that are now providing habitat to ensure this potential is turned into reality through a combination of planning and practical management. In this way we can ensure the 'bonus effect' remains in place and stays resilient into the future.  

Support for the case study is gratefully acknowledged from Brian Mason Scientific & Technical Trust, NIWA, IPENZ Rivers Group, Ngāi Tahu Research Centre and the Marine Ecology Research Group at UC.

REFERENCES

Orchard, S., Hickford, M. J. H., & Schiel, D. R. (2018). Earthquake‐induced habitat migration in a riparian spawning fish has implications for conservation management. Aquatic Conservation: Marine and Freshwater Ecosystems, 28(3), 702-712. doi:10.1002/aqc.2898

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