File photo / NZ Herald
Above the waters of the Hauraki Gulf, a marine farm might appear only a tidy row of racks, or a small bunch of ropes and buoys dotted against the blue.
But below the surface lie unseen clusters of oysters or mussels - and the hope for a sustainable economy potentially worth hundreds of millions of dollars more to the Auckland and Waikato regions.
Aquaculture in the gulf is becoming increasingly important not just for New Zealand's primary industry economy, but for the wellbeing of the communities that depend on its survival.
With nurture, the industry forecasts nationwide growth of aquaculture in New Zealand could reach $1 billion by 2025.
Much of that growth would come from the gulf, which presently provides nearly 60 per cent of the country's farmed oysters and a quarter of its mussels.
Their combined value in the gulf is worth around $60 million, contributing to the economy around $170 million and providing more than 900 jobs in the region.
"When people talk about 'the economy' I think they have a picture of large companies in big cities," said Callum McCallum, a long-time leader in the oyster industry and chairman of Sea Change's aquaculture roundtable.
"But aquaculture provides jobs and turnover in coastal communities that really need them, like Coromandel and Clevedon - so when we talk about 'economy' we're talking about benefits to local people in the Hauraki Gulf."
In the gulf today, there are over 1270ha of mussel and oyster farms - the equivalent space of around 1270 international rugby fields.
The oyster industry took off from the moment in the early 1970s that marine farmers in Mahurangi Harbour, north of Auckland, discovered a new type of oyster growing among the native rock oysters they'd traditionally farmed.
The Pacific oyster, thought to have been carried to New Zealand on the hulls of freighters from Japan, was first seen as a nuisance by farmers who tried to eradicate it. But as it could grow three times bigger and faster than its native counterpart, it soon became an industry mainstay.
In 2010, a herpes virus nearly wiped out the country's Pacific oysters, but industry breeding programmes had helped it recover.
The industry also now has its own oyster hatchery and was working to develop a herpes-resistant strain, Mr McCallum said.
"The natural spat has also become more resistant to the virus, so after four poor years, we are starting to produce better volumes of oysters."
By the end of the 1970s, the first mussel farm had been established at Waiheke Island, before mussel farming in the Coromandel began in the early 1980s. The relatively clean waters of the gulf were ideal for oysters and mussels, which as filter feeders pump out water after sucking in tiny drifting plants.
Mr McCallum said because they performed a service in the ecosystem, there wasn't a clash of environment and economy.
"The industry has carried out a lot of research to prove that aquaculture in the gulf has very little negative effect on the environment and is hugely beneficial for water quality."
According to results of a Colmar Brunton survey commissioned by the Ministry for Primary Industries this year, most Kiwis agree.
Seventy-three per cent had positive views of aquaculture, while 91 per cent believed New Zealand should look for opportunities to sustainably grow the industry.
As mussel farms acted like artificial reefs and attracted snapper and other fish, aquaculture had also attracted fishing and charter fishing boats.
"That means more jobs and more income for local communities," Mr McCallum said.
The Auckland region has about 251ha of existing marine farms, and last year there were applications under way for a further 4600ha for farms and spat catching.
Most of these are in the western Firth of Thames, and about half of them were transferred to the Waikato Regional Council when the boundaries were re-aligned.
The 1900ha of space allocated in Waikato includes farms already operating. Nearly 400ha for finfish farming has also been allocated.
Those who apply for consent from councils must prove their operation will have little environmental impact, as well as an undue adverse effects test required by the Ministry for Primary Industries.
Farms are also regularly checked for "trigger points" that can signal environmental concerns, such as water quality and what animals are living on the floor beneath the farms.
Environmental groups have expressed specific worries, including whether there was enough water movement around farms, or if they could negatively affect other species.
Despite the relatively tiny area that farms make up in the gulf, there had been some rare cases of threatened Bryde's whales becoming entangled in mussel spat collecting lines.
"In the past we've been engaged in endless debates about where marine farms should go and where they shouldn't, but now we are looking at the big picture and seeing the benefits to the environment and to coastal communities," Mr McCallum said.
The roundtable's aim had been to determine the role, needs and impact of aquaculture in the gulf.
"The process has been really encouraging because for the first time, we have people from every viewpoint around the same table talking positively about the industry, its benefits and its future in a sustainable world," he said.
"One of the key needs for aquaculture is research and experimental provisions that allow the industry to test the benefits and effects of farming new species.
"And the gulf would be an ideal location."
To have your say on aquaculture in the Hauraki Gulf click here.