An Auckland Council plan to remove the historic weir across the Mahurangi River, close to the Bridgehouse bar and restaurant, has infuriated locals who insist it must stay.
But Auckland Council’s senior advisor for freshwater biodiversity Matt Bloxham is equally adamant the weir must go.
The weir was originally built to facilitate the supply of water to the Wilson cement works and is about 100 years old.
Mr Bloxham says the physical height and speed of water crashing over the weir make it near impossible for native fish – particularly whitebait – to scramble over the weir to get upstream to spawn.
He says the weir threatens the long-term survival of the fish in the river.
He adds that removal of the weir is a permitted activity that requires no resource consent or public notification.
But following a public outcry from locals who treasure the weir for historical and aesthetic reasons, Rodney Councillor Greg Sayers says he has persuaded Council to suspend plans to dismantle the it until more public consultation has taken place.
It is expected a public meeting will be held in the Warkworth Town Hall early this year.
Meanwhile, Mr Bloxham remains unimpressed by arguments that insist the weir should stay for aesthetic reasons.
“Those sorts of attitudes make me pretty cross, because the weir is impacting the entire fishery and will continue to have an impact for a very long time,” he says.
The problem is compounded by a second weir – known as a gauging weir – further upstream, close to Mahurangi College, which is an even more severe impediment to fish movement.
Council is already well advanced with efforts to replace the gauging weir with a “crump” weir, which will allow fish to cross it more easily.
But Mr Bloxham says one of the consent requirements for the gauging weir is that there must be a “catch and haul” programme, whereby fish are gathered downstream and released further upstream to ensure the fish population survives.
Mr Bloxham says once the gauging weir is removed, the catch and haul programme will end. He says therefore it is urgent to remove the Wilson weir.
Mr Bloxham adds that some have suggested using fish ladders to assist fish to get beyond the weir, but says these are expensive to maintain and subject to vandalism and flood damage.
But locals with strong connections to the Mahurangi River have rubbished Council claims.
The manager of Warkworth-based whitebait farm Manaki, Paul Decker, says while it’s true some weirs present difficulties for fish, this is not true of the Wilson weir.
“They have no trouble getting up, I have seen them get up,” he says.
Mr Decker says the declining number of whitebait in the Mahurangi River is due to the increasing amount of sediment flowing into the river from contaminated water, which has created an environment inhospitable to fish.
Another big killer of whitebait is hot water. As trees have been cut down along the riverbank, more direct sunlight has hit the water, raising its temperature and killing fish.
The weir looks spectacular following heavy rains. Photo, Ian Anderson.
Mr Decker says if the weir is removed, the deep water it created will become shallower, heat a more quickly and expedite the demise of whitebait.
Peter Thompson, of the Mahurangi River Restoration Trust, agrees the decline in whitebait cannot be blamed on the weir.
“Back in the fifties and sixties, we used to get heaps of whitebait and the weir was still there.” he says.
The trust is currently engaged in a $5.1 million project to dredge the Mahurangi River.
Mr Thompson says the aim is to reap a host of aesthetic and recreational benefits for generations, but removing the weir would take away one of the river’s most attractive features.
Chair of the steering committee of the Jane Gifford Trust Dave Parker says the loss of the weir would be disastrous as it has enormous historical significance for the town, at various times serving not only the cement works but also a flour mill, jam factory and sawmill.
“I can remember as a schoolkid we used to swim at the weir, and when the circus came to town the elephants used to go in there for a wash,” he says.
Meanwhile, the president of environmental group Mahurangi Action, Tessa Berger, says the group is assembling a panel of experts for a Town Hall Talk on February 13 to discuss the issue.
“Any aesthetic value of the weir is probably outweighed by the negative impact on biodiversity, but that presumes that there are no acceptable alternatives that might allow the structure to remain,” she says.