A story of a New Zealand river - Waipu community takes bio-blitz action

Bjorn Leigh of the Department of Conservation shows critters caught in Waipu's bioblitz. Photo / supplied

A bio-blitz held to gauge the health of the Waihoihoi river will be used as a baseline for future conservation work.

The Waihoihoi river flows from the Brynderwyn Ranges down through native bush, forestry, farmland and lifestyle blocks through to the township of Waipu.

It is one of the tributaries which feeds into the Waipu river and the popular fishing and recreational areas of Bream Bay on the east coast of Northland.

The organisers of the comprehensive biodiversity survey are hoping that all of the upstream neighbours will join their efforts to improve the health of the stream, with the survey a way of raising awareness in the rural community.

It is part of the Waipu River Walk project, which was allocated $100,000 in August 2019 by the Whangarei District Council.

The Waipu Community-Led Project Committee was formed in March last year with submissions and feedback for how the funding could be spent. The winning project was the Waipu River Walk proposal. The chairperson of the committee is Lydia Draper.

The first stage of the walk is opening soon, with the trail starting at Waihoihoi Park and following the river to Nova Scotia Drive, where it will connect to an existing footpath. From there, pedestrians can loop back to the park through the township, taking about an hour to complete.

The initial bio-blitz was conducted by the Waipu River Walk's ecology team alongside about 20 enthusiastic Bream Bay College students and citizen scientists from the community. Representatives of the Department of Conservation, Northland Regional Council and Patuharakeke's Taiao unit helped run the day in late October.

Bjorn Leigh of the Department of Conservation. Photo / supplied

Multiple stations were set up to record the different categories of wildlife in the area. Water tests were also taken to survey the river's health.

Ari Carrington, of the Patuharakeke environment unit, said he ended up running the insect workshop.

"It was really interesting as I don't normally get to look at the environment to that level of detail. We had Auckland University entomologist and lecturer David Seldon on the phone as he was unable to cross the border for the event.''

Seldon's research speciality is taxonomy: discovering, categorising and naming beetles unknown to science. In 2019, in the Waipu Gorge area just above Piroa Falls, he found a large black beetle from the genus Mecodema, a new species he named Mecodema xylanthrax. The species name, xylanthrax, means coal or charcoal.

"It was great because he could check our insect photos and identify them for us," Carrington said.

Among the critters to be shaken from the trees in the area were cockroaches, leef beetles, an assortment of spiders including meshweavers, long-jawed orbweavers, comb-footed spiders, bronze hopper jumping spiders, earwigs and a longhorn beetle.

A net in the river during the survey period yielded freshwater keewai or crayfish, long and shortfin tuna, yellow-eyed mullet, inanga, smelt, shrimp, common and giant bullies, Australasian marine gobies, parore and crabs.

Three bird surveys during the day and night had identified a mix of common garden birds and coastal birds.

Bio-blitz organiser Peter Grant said the event was "like a stocktake", where the existing wildlife was catalogued, and repeat surveys in future would be able to show improvements in river health and biodiversity in the water and on the edges.

"It was the first time a proper survey has been done. It's a chance to find out what needs to be done to improve the health of the river.

"Upstream in the Aharoa river, which is another tributary, the drinking water for Bream Bay is collected.

"There are a number of farms, and we know many are doing their bit by trying to fence off riparian areas from stock.

"But there is still more that can be done,'' he said.

Erosion was a constant challenge on the river banks and more planting was needed for shading the water.

A weed management plan has been drafted by Sara Brill, co-ordinator of the Weed Action Piroa-Brynderwyns group. The plan aims to prioritise weed control on the river's edges, with wattle, privet, gorse, hawthorn, alligator weed, periwinkle, pampas, bushy asparagus and arum lilies identified as key invaders.

The river water was found to be "maxed out" on nitrate levels and high in phosphate levels.

"The nitrate was as high as the meter goes, so we don't really know how bad it was.

"It was just after a significant rainfall event, and there was a lot of sediment,'' he said.

Grant said an inspiration has been the tales from elderly Maori who can remember spearing kingfish near the Waipu town centre.

"Wouldn't that be wonderful to see again one day?''