My Account
Experts on opposing sides of the weir debate clashed before a packed meeting at the Warkworth Town Hall on February 13.
The controversy arose after it emerged that Auckland Council planned to remove the historic weir on the Mahurangi River, near the Bridgehouse Bar and Restaurant, in an effort to save whitebait. It was claimed that the fish were unable to scramble over the weir to spawn.
But many locals adamantly insist the weir poses little threat to whitebait and ought to be retained for historical and aesthetic reasons.
Council’s advisor for fresh water biodiversity, Matt Bloxham, presented the case for the weir’s removal, while the manager of Warkworth-based whitebait farm Manaki, Paul Decker, argued for retention.
Also presenting was the chair of the steering committee for the Jane Gifford Trust, Dave Parker, who spoke on the weir’s historical significance.
Mr Parker blasted Mr Bloxham for failing to consult with interested community groups, such as the
Warkworth River Bank Enhancement Group, the Mahurangi River Restoration Trust and the Jane Gifford Trust over plans for the weir’s removal.
“It’s unfortunate the Council’s biodiversity department really appears to have no interest in things to do with our heritage,” he said.
Mr Bloxham defended the “lack of consultation” charge, saying a survey conducted at a booth at last year’s Kowhai Festival revealed that more than 80 per cent of respondents favoured removal of the weir to allow fish to pass. He went on to reiterate arguments for the weir’s removal.
He said inanga – the chief whitebait species in the river – were poor climbers and the weir was too big a hurdle for them to cross. This meant that they were denied 100km of stream habitat above the weir.
Once they were halted at the weir, they became easy prey to predatory birds and whitebaiters. This was a concern because inanga are a threatened species in the region.
Mr Bloxham said Council had considered alternatives to the weir removal such as fish passes or ladders, but these had a high failure rate, were expensive to maintain, difficult to ensure an appropriate water flow across them and were subject to vandalism and flood damage.
He said the New Zealand Fish Passage Guidelines advised that weir removal was the first option for maximising fish passage.
“I’m very keen on cultural heritage, but not when it has such a huge impact on our natural fauna,” he said.
In response, Paul Decker agreed that inanga were not great climbers, but he had personally witnessed them climbing over the weir. Noting that the weir was more than 100 years old, he said if it had truly stopped whitebait travelling upstream, then they would have been extinct in the river by 1907.
Mr Decker said there were other reasons why whitebait struggled in the Mahurangi River, notably rising water temperatures and a high pH level.
He said there was no evidence to suggest removing the weir would improve whitebait numbers.
“My proposal is the weir stays,” he said, to hearty applause.
Mr Decker suggested instead the installation of two fish passes, which he said would cost “a mere $500”. He disputed Mr Bloxham’s concerns about passes, saying passes on nearby Mill Stream worked well, had never been vandalised and had never needed maintenance.
He said data could be collected to determine if the passes were effective. If they were ineffective, only then would it be appropriate to consider removing the weir.
Mr Decker and Mr Bloxham were joined by planner Shane Hartley, of Terra Nova Planning, for a panel discussion and to take questions from the audience.
One speaker contested Mr Bloxham’s view that inanga were being denied 100km of stream habitat, since there were major waterfalls just a few kilometres upstream that presented a far more serious impediment to fish passage than the weir.
Another speaker backed Mr Decker’s view that more data was needed before the weir was removed.
But yet another speaker, Paul Franklin, a NIWA fresh water ecologist, supported Matt Bloxham’s views on fish passes, saying that to get them to work on the Mahurangi River would be a complex and expensive process.
Asked to comment from a planning perspective, Mr Hartley said Warkworth’s planned rapid expansion over the next 25 years would increasingly see the “character lines” that made the town special get rubbed out, and he urged caution over the weir.
“We rush into these things because the ecological approach is to say, ‘Let’s fix this in a dramatic way’, but you have got to set against that the balancing issue of heritage,” he said.
“If this was any old weir I’d say, ‘Fine to let it go’. But this is a substantial structure and the decision cannot be made lightly.”
Following the meeting, Council general manager of environmental services Gael Ogilvie said Council’s next step would be to complete an independent technical study of the weir to provide a factual basis for further discussion. Mr Decker’s help would be sought to help scope the study, which would then be outsourced to an independent freshwater ecologist. Ms Ogilvie said Council would fund the study. The cost would depend on the scope of the study.
