9 April 2014

River dwellers to shift to allow cleanup

Some river dwellers are undergoing a temporary shift as the revitalisation of the Avon River continues from this week.

As part of the development of the 3.2km-long Avon River Precinct, the stretch of river between the Montreal Street Bridge and Colombo Street will be subject to in-river works that includes clearing built-up sediment to improve the health of the river.

But before that work happens, longfin eels (Tuna kuwharuwharu) that inhabit that stretch of water – some estimated to be as old as 80 years – need to be moved out of the way.

EOS Ecology aquatic scientist Shelley McMurtrie says a method known as “electric fishing” will be used to capture the eels before they are shifted to another part of the river such as Watermark – the first completed stage of the Avon River Precinct. The eels will be returned to the stretch of water they inhabit once the work is completed.

“Electric fishing does not harm the fish but temporarily stuns them to enable trained ecologists to capture and relocate them,’’ Ms McMurtrie says.

“Some fish will move out of the way of the in-river works and then move back in when we are done. But others burrow into the sediment or try to hide along the banks or in aquatic plants, which is why we either electric-fish parts of the channel, or fish the sediment after it’s been collected. So far this year we’ve rescued over 150 fish from the sediment - eels, flounder and lamprey - and returned them to the river.”

In addition to the relocation of the eels, it is expected that bluegill bullies – considered rare locally - will be temporarily shifted from the area below Mill Island and around Victoria Square when work is done in those parts of the river.

“We are enhancing the river for these animals so it’s important to make sure they are still around to benefit from it,” says Ms McMurtrie.

This phase of in-river works to Colombo Street will take place during April and May, and the work will continue through to Fitzgerald Avenue after the trout-spawning season. The works promote ecological improvements by removing excessive silt layers, including liquefaction sand, and forming low level plains to improve water flow and species habitats.

Christchurch Central Development Unit director Warwick Isaacs says the work being done to improve the river quality is about making the river into a world class feature for the city.

“We have seen from the work done at Watermark what a difference it can make, and it will be fantastic to see that expanded through the whole length of the Avon River Precinct.”

More on the Avon River Precinct can be found at www.ccdu.govt.nz.

ENDS

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