Spawning habitats hold hope for inanga

A North Canterbury stream could soon be teeming with inanga/whitebait.

Inanga spawning habitats have been restored in Taranaki Stream at Waikuku Beach, giving hope the stream will return to being a thriving environment.

Waimakariri District Council water environment adviser Sophie Allen says inanga were under threat due to climate change and changing coastal environments.

“The question is often asked whether inanga are a freshwater species or a saltwater species and the answer is they are both.

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“Their spawning areas need to be on the edge of saltwater and the freshwater, but as coastal environments change, where will these areas move to?”

At Taranaki Stream, the banks had risen over time and the grasses had been eaten away by farm animals.

The council now owns the land, with the stream fenced off and the banks lowered and replanted, to provide six regenerated spawning habitats.

The earthworks happened about 18 months ago, with the planting completed last year.

Planning was essential as the right plants and grasses were needed to ensure the eggs stayed damp and did not get sunburnt, Allen said.

“They have to be the right plants. Inanga like plants with lots of stems and dense roots.

“It is still early days, but when the plants grow to full size over the next year or two we will get a better idea if we have created a deluxe habitat for the whitebait.

“The first survey is saying we have got some spawning returning, which is a good start.”

The inanga spawned about Easter.

They swam into the habitat at high tide and wriggled up into the grasses to lay their eggs.

“They like to spawn together in a shoal. The water can go white when they all release their eggs together,” Allen said.

The eggs hatch a month later, with the baby inanga being washed out to sea.

There they feed until they are about 6 months old, and return to the freshwater in the spring.If they avoid the whitebait nets, they can grow to 80mm to 110mm by the time they spawn as 1-year-olds.

“Some people do question whether we should be catching them at all, but the biggest threat is not having a habitat for spawning because the stream keeps changing and climate change has exacerbated that,” Allen said.

The projected was jointly funded by the Waimakariri District Council and Environment Canterbury, and supported by the Waimakariri Water Zone Committee.