Open ocean farming project set to boost New Zealand exports

Cawthron Institute aquaculture scientist Kevin Heasman with a proposed advanced prototype of a mooring system to be used ...
Sara Meij

Cawthron Institute aquaculture scientist Kevin Heasman with a proposed advanced prototype of a mooring system to be used at open ocean farms.

Nelson's Cawthron Institute is at the helm of a groundbreaking open ocean shellfish farming project that could boost New Zealand aquaculture exports by tens of millions of dollars.

Led by Cawthron Institute aquaculture scientist Kevin Heasman, the five year project recently received $6 million from the Ministry of Business, Innovation and Employment.

Heasman said the project aimed to revolutionise the current open ocean farming structures to make them more efficient and low maintenance.

It was the first research project in the world to look at developing new technology appropriate for the offshore environment, he said.

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Heasman said New Zealand was the most efficient at mussel farming producer in the world and the project could up the game even more.

"We are it, we're the cutting edge, everybody else is watching us.

Increasing volumes of high end aquaculture products from a number of shellfish species could boost exports by tens of millions.  

The new technology could be sold on to other mussel farmers around the world.

One of the main differences between inshore and open ocean farming was the amount of energy produced by surrounding water impacting on the mussel lines, Heasman said.

Inshore mussel farms consist of floats on the surface with mussel lines directly attached to them.

Current offshore farms consist of fewer floats on the surface and the backbone of the farm under water, with mussel lines attached.

"That way when waves are coming past there's fewer floats to transfer the energy to the backbone," Heasman said.

"Less energy means less maintenance and potential product losses." 

Heasman said the aquaculture industry had expanded their inshore farming offshore, but the structures weren't really suitable for open ocean waters.

"And that's got its limitations obviously."

Heasman said open ocean farming wouldn't replace inshore farming. 

He said the current open ocean farming structure was very labour intensive because of the regular check-ups and amendments needed.

The new patented system for the open ocean farms would include only minimal buoys at the surface and a line of subsurface floatation structures at 10 metres to which mussel lines were attached.

Moorings would attach the subsurface long line with the ocean floor.

The open ocean farm the research and prototypes would be used on was located 8 kilometres off shore from Opotiki in the Bay of Plenty and was spread over a 3800 hectare area. 

Prototypes of the structure would be tested in a very large wave tank, about the size of an olympic swimming pool, at the University of Hannover.

Heasman said the energy distributed in the open ocean was "huge".

"That particular farm we're working on has had three times last year with waves exceeding nine meters.

"So you've got to start getting these things under the water and submerged because the amount of energy as you go deeper in the water is reduced significantly." 

Heasman said the Opotiki community was behind the project, since it would supply the small town with permanent jobs instead of seasonal ones. 

"It will provide a huge percentage of jobs for a place which is struggling to find employment."

Heasman said the open ocean farms also can function as nurseries as it's a midwater reef, attracting fish to the area. 

"Fisherman are catching all sorts of fish that they really had to search for before."

He said whales can't get entangled in the mussel lines as they are all under pressure. 

The farm structure also wouldn't impact on boats as the farms that were currently considered were all outside of normal navigation routes and would have navigation marks on them, Heasman said.

He said small boats would be able to drive over the backbones of the farm because they would be submerged.

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