The Canterbury earthquakes devastated the lower reaches of the Heathcote River / Ōpāwaho and its mouth at the Avon-Heathcote estuary.
After four years of recovery, one beneficiary may be whitebait. Adult whitebait lay their eggs in streamside vegetation in the area where saltwater mixes with fresh river water, says University of Canterbury doctoral researcher Shane Orchard.
Orchard’s PhD research, supervised by Professor David Schiel, investigates the vulnerability of coastal conservation areas to dynamic changes such as sea level rise. He is using earthquake effects to simulate the type of issues that might occur with climate change.
“Because of uplifting and liquefaction at the river mouth, the local pattern of saltwater intrusion is thought to have changed and large numbers of whitebait eggs have now been found in the lower Heathcote River, closer to the estuary than ever seen before.
“I am exploring the salinity environment in the lower reaches of the Christchurch rivers to get a better picture how this might affect whitebait spawning sites and ways they can be protected.
“A surprising additional result has been finding these new sites for whitebait eggs in areas where none have previously been found. This result shows that these important sites have indeed been on the move.”
With Dr Mike Hickford and Professors Schiel and Bryan Jenkins, the researchers are investigating better ways of protecting and improving spawning grounds around the city over the long term. This includes identifying opportunities for remediation and the best management approaches to protect important parts of the waterways.
Their focus is on methods for coastal conservation. Whitebait have been in decline and management is an ongoing conservation issue.
Their work is supported by the Ngāi Tahu Research Centre, the University of Canterbury, Marine Ecology Research Group and the Waterways Centre for Freshwater Management, and Lincoln University.