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Canterbury salmon tagged in Niwa study

NZ Newswire logoNZ Newswire 28/12/2016

Phil Jellyman is jet boating up the Waimakariri River in Canterbury this summer.

But rather than being a holiday excursion, Mr Jellyman is on a scientific mission to look for salmon.

The NIWA freshwater fish ecologist is planning to implant acoustic tags on the fish to find out whether irrigation schemes are affecting their migration to spawning grounds up river.

Along the river, he will install about 25 receivers that will gather information transmitted from the tags.

The 151km-long Waimakariri has a reputation as one of New Zealand's top salmon fishing rivers.

Irrigation schemes allow farmers to extract water from the river for most of spring and summer, but recent schemes have been targeting floodwaters for harvesting.

However, little is known about how that could affect the movement of salmon.

"We want to know what sized flood is prompting their movements up the river and how their upstream migration to spawning grounds is affected when water is taken from the river," Mr Jellyman said.

He said salmon typically migrated when the water was dirty after the peak of a flood.

This was probably because the dirtier floodwater gave them more cover, was slightly cooler and tapped into some innate instinct they had.

Mr Jellyman said the aim was to find out how much the flow harvesting by irrigation schemes could potentially delay the upstream movements of these fish.

"The salmon are coming in from mid-December onwards to get to their spawning grounds from April onwards," he said.

"The upstream movement of salmon is happening at the same time that irrigation intake is at its peak."

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