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Maygrove Lake in Ōrewa may be a stormwater treatment pond, but it is also an attractive lake, valued for its aesthetics by residents, who have been voluntarily clearing it of weed and debris for years.
Those residents, members of Maygrove Residents Association, are hoping that the wet and difficult job will be largely taken care of in future by 10 grass carp, which will be released in the lake in the coming months.
Fast growing introduced weed species, including oxygen weed, thrive in the lake. The carp feed on these, keeping the water clear.
Grass carp were first introduced to the lake in 2007. They were all washed away by floods until barriers were put in place before a further release in 2015. In 2020 Auckland Council cancelled its contract with the owner of those fish, and the contractor therefore removed them from the lake.
Residents association member Marie Walding has been helping look after the lake for a decade. She says getting carp back into the lake since 2020 has required persistence on behalf of residents who live near the lake, in particular Jerry Paterson. Covid restrictions, and the need for Department of Conservation approval, also delayed the process.
Walding says without the fish present, around 40 volunteers have had to do major cleanups of the lake twice a year.
Some would wade in, clearing what they can and others work around the margins.
“We’d do it more often, but council would only pay to take the weeds away twice a year,” she says. “And some of it was too hard for us to do.”
Auckland Council senior Healthy Waters specialist Coen Ursem says this time council is purchasing, not leasing, the fish, which he says is a more economical way to maintain the lake.
“We will initially introduce 10 grass carp to Maygrove Lake,” he says. “As the lake is a stormwater treatment pond, the number of carp needs to be in balance with that stormwater treatment function.”
Once the carp have been released, the fish and pond condition will be monitored by council.
Acknowledging the work that locals do in regular clean-ups, Ursem says that important maintenance work is undertaken by council.
“Maygrove, like the other 300 stormwater ponds in north Auckland, are included in Healthy Waters’ maintenance programme,” he says. “Council’s maintenance contractor undertakes monthly inspections of Maygrove Lake, focusing on inlets, weirs, grills and removing rubbish. They take photos, report on vandalism and erosion. We also remove aquatic weeds that are impeding flows and or have been taken out by local volunteers.”
He says the fish are being introduced because council can see how much pride the locals have in the lake, and appreciates their voluntary clean-up work.
“The aquatic weed removal is mainly for aesthetic purposes, so it is not feasible or a good use of ratepayers’ money for contractors to weed the entire lake,” Ursem says.
