Plans for Waitaki to Spoil Catches

By STAFF, Herald

Meridian Energy’s plans for the Waitaki River will not harm salmon habitat but the North Bank Tunnel will make catching the fish harder, water hearing commissioners were told yesterday.

The Cawthron Institute’s Dr John Hayes said stable flows of about 150 cumecs would be good for salmon angling habitat and the fishability of prime angling spots.

However, less flow means less sediment and clearer water which would make catching salmon harder.

Dr Hayes based his argument on modelling and experienced angler assessment of salmon angling lies (good fishing spots).

The lies have deeper water where salmon can lie and wait.

Under four controlled flow regimes expert anglers assessed the lies along a 10km strip of the river.

The greatest number, area, and quality of salmon angling lies occurred around 150 cumec flows and the optimum range was between 130 and 200 cumecs.

Too much flow meant the fish would not stay in the lie, and the river became too hard to access and wade.

Too little flow meant the river bed made the water turbulent in the lies and less attractive for resting fish.

While the Waitaki water allocation plan’s flow regime of 140 cumecs was the best for salmon angling habitat the North Bank Tunnel, the regime’s flows during January, February, March and April were comparable.

He said median flows were more significant than minimum flows.

“What is most important are the flows that the river is at for most of the time.”

Dr Hayes said below the tunnel outfall at Stonewall anglers would still have a big river experience. This was where 64 per cent of salmon anglers fished.

The reduced flow from Stonewall to the Waitaki Dam could mean less encroachment by vegetation and high flows. This would allow better foot access.

He was of the opinion at 140 cumecs from the dam to Stonewall the river would be of similar scale to Canterbury’s other alpine fed rivers.

Any warming of the water, where flow was reduced beside the tunnel, would not affect the salmon, he said.

However, increased water clarity would result due to less flow to pick up sediment and most big flows being diverted.

This would make catching a salmon harder.

Dr Hayes said using lighter line and smaller lures may help mitigate this.

There was the possibility of varying flow during angling season, however the affect on aspects of the environment needed to be weighed up. Removing gorse and broom from the river may help free up a source of sediment and there was the option of adding sediment to this stretch of the river.

While the effects on salmon angling habitat were considered minor the reduced catch rate caused by clearer water would be more significant.

Central South Island Fish and Game officer Mark Webb said water clarity looked like being a major issue for anglers.

He was unconvinced 150 cumecs was the optimum flow, and if it was, then the flow regime was well below it during angling. Only the minimum flow in February met the optimum criteria.

“If at 150 cumecs it’s too clear then at 120 or 130 cumecs it will be even clearer,” he said.

n Herald Staff

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