Negative Impact on Salmon Fishing

By STAFF, Herald

A 100 cumec minimum flow in the lower Waitaki River will reduce the quantity and quality of salmon angling habitat, an expert witness said yesterday.

However, the 100 cumec minimum flow proposed by Hunter Downs Irrigation was still an improvement on the 80 cumec minimum flow which had applied in the past, according to Cawthron Institute senior fisheries scientist John Hayes.

Independent commissioners Professor Peter Skelton, Mike Bowden and Dr Greg Ryder yesterday continued hearing an application by Meridian Energy and the South Canterbury Irrigation Trust for consent for Hunter Downs Irrigation to take water at a peak rate of 20.5 cubic metres from the lower Waitaki River, and seeking to reduce the minimum flow from 150 cumecs to 100 cumecs.

Mr Hayes gave evidence on flow requirements of salmon angling in the lower Waitaki River, and the effect of the proposed scheme on salmon angling.

Mr Hayes said the effect of the 100 cumec minimum flow on salmon angling habitat would be for a limited time, because minimum flows generally occurred most frequently before the peak of the angling season.

The effect would be noticeable during dry years when the flow would be drawn down to 100 cumecs for much of the first two months of the salmon season — January and February. However, it would be much less during average years, when the flow will be drawn down to 100 cumecs for a few days in January to early February.

Mr Hayes said the effects on salmon angling habitat needed to be put in context of flow conditions that would occur most of the time.

“The median flow, which represents the flow condition salmon anglers experience most of the time, will not change appreciably under the 100 cumec minimum flow regime. However, effects will be noticeable by salmon anglers during dry years.”

Flow and water clarity would still be variable, which was good for salmon angling, and water temperature would not change significantly as a result of the water take proposed by the Hunter Downs scheme, Mr Hayes said.

NIWA fisheries biologist Don Jellyman gave evidence on the impacts on native fish in the lower Waitaki River.

Mr Jellyman said the reach from the proposed intake at Stonewall to the sea contained the greatest diversity of native fish, with eight species from the mainstream, and a further nine in the lower- estuarine reach and the lagoon.

Two species were listed on the Department of Conservation’s “threatened” species classification — the longfin eel and the Canterbury mudfish.

Mr Jellyman said if flows of 100 cumecs persisted for several weeks, there would likely be a small reduction in the numbers of native fish, especially torrentfish.

In the unlikely event of substantial mortality associated with low flows in a particular year, numbers of fish would return to normal the following year after the spring recruitment of juveniles.

n Herald Staff

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