Trout in pool point to consent change

Ross Dungey's observation of 77 trout in a pool of the Wairau River prompted the Otago consultant biologist to recommend an addition to conditions of consent for TrustPower to operate a hydroelectric power scheme on the Wairau River.

Conditions of consent were set by the Marlborough District Council-appointed panel, which in 2007 gave the electricity generation and retail company approval to build the power scheme.

That decision was appealed, and the application is now being reconsidered by the Environment Court in Blenheim.

Mr Dungey, an expert witness for TrustPower, saw trout build-up in the Hillersden reach of the river during an extended dry period in 2008 as highlighting the risk of low flows inhibiting spawning migration. Concerned that reduced flows through the river resulting from the hydro scheme could more frequently prevent spawning fish from swimming upstream, he suggested that a condition be imposed to avoid the problem.

Commissioner Alex Sutherland observed that existing conditions of consent did not include this provision. Mr Dungey, who presented his evidence on Tuesday this week, was requested to draw up an appropriate condition by the following morning. Yesterday he was cross-examined on his suggested low-flow trigger point for survey.

Forty consecutive days with continuous flows of 15 cumecs or less below the Goulter confluence was recommended by Mr Dungey as a trigger for TrustPower to survey the Hillersden reach by air. If 25 or more trout were seen in a single pool, the next fresh should be allowed to flow down the diversion stretch of the river rather than through the power scheme, enabling the fish to continue upstream.

The condition would apply during the spawning season from April to June.

If fish remained blocked, freshes should be released down the river until they had escaped the pool.

Mr Dungey recommended that TrustPower's draft aquatic management plan be amended to flag the potential for the scheme to impede trout spawning due to abstraction during low flow periods.

Fish & Game lawyer Maree Baker pointed out that there were also salmon in the Wairau and asked whether they should also be included in the consent condition. Mr Dungey said that no, they tended to migrate in much "flashier" conditions than trout so were unlikely to be held up.

Mr Dungey concluded that angling opportunity in the Wairau River was "remarkably similar" at the 11, 18, 42 and 700 cumec flows he surveyed.

Asked by Ms Baker whether he was aware that most fish were caught in the Wairau between 20 and 80 cumecs, he responded that he was not looking at whether or not waters were suitable for angling rather than use.

The 700 cumec flood flow would not provide good angling, he agreed with Ms Baker. However, even at this flow he still found areas of back eddies and pools that were still available.

Mr Dungey agreed that his study was restricted to observing relevant angling features, such as amount of ripple, run and pools under different flows. The overall experience, including factors such as solitude, was not considered.

- The Marlborough Express

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