Ecological experiment leads to spawning success

When Kaikōura inanga (whitebait) needed a hand in hatching last month, Kaikōura’s zone team were right there ready to assist.

It began when University of Canterbury researchers discovered a number of inanga spawning sites in the Lyell Creek near the Kaikōura i-site.

They were there as part of their ‘RECOVER’ earthquake recovery project, conducting surveys of Kaikōura’s coastal streams to establish where whitebait may be spawning.

They found inanga eggs in streamside grasses near the i-site which were likely laid during a rain event which had brought the stream level up about 400mm. The water had since dropped leaving the eggs stranded in the grasses.

Hatching a plan to save inanga eggs

With no sign of rain coming, Environment Canterbury’s Kaikōura works supervisor Peter Adams devised a plan. Would it help if we block the stream mouth to lift the water level back up to the location of the eggs?

Shane Orchard from the university agreed it would likely do the trick.

Leading up to the planned ‘hatch day’, Shane had monitored the eggs to make sure they were still there and ready to hatch. The day before, the UC team hatched a few out in lab just to be sure.

They also experimented with a sprinkler to simulate a heavy rain event at one of the sites. That produced a few larvae but the majority of the eggs needed a decent soak.

Using a small excavator, Peter closed off the Lyell Creek which raised the stream level enough to cover most of the eggs with water.

The next morning the spawning sites were re-measured and very few of the eggs remained unhatched. The stream built enough pressure that it reopened naturally.

Gaining a better understanding 

Kaikōura project delivery officer Heath Melville said the findings in this experiment has helped gain a better understanding of how we can assist inanga, particularly with changes to the landscape post-quake.

“There is still a lot to learn about New Zealand’s indigenous freshwater fish species. As more information becomes available it can help inform drainage and river protection works.

“With mahinga kai protection and enhancement becoming a priority in the community, this experiment aligns beautifully by assisting several thousand little fish in need,” he said.

Find out more about Mahinga kai

Inanga spawning sites in the Lyell Creek near the Kaikōura i-site

Inanga spawning sites in the Lyell Creek near the Kaikōura i-site

Using a small excavator, Peter closed off the Lyell Creek

Using a small excavator, Peter closed off the Lyell Creek.