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Source: University of Canterbury

03 July 2019

Aotearoa New Zealand is a world leader in shellfish farming and Professor Keith Alexander is part of a team researching ways to keep the country at the forefront.

  • Doctoral student Sam Godsiff and Professor Keith Alexander are part of a team researching ways to keep New Zealand at the forefront of shellfish farming and ensure shellfish supply into the future.

Aotearoa New Zealand is a world leader in shellfish farming and Professor Keith Alexander is part of a team researching ways to keep the country at the forefront.

Mussel and shellfish farming is a billion-dollar industry and is crucial to meeting the world’s food demand in the 21st century. It is also an important part of Aotearoa New Zealand’s history and, more importantly, its future.

This is why Professor Keith Alexander in Te Rāngai Pūkaha | College of Engineering and PhD student Sam Godsiff are working with Cawthron Institute to study methods to improve the efficiency of mussel and other shellfish farming in the open ocean.

Cawthron Institute is Aotearoa New Zealand’s largest independent science organisation specialising in aquaculture, biosecurity, marine, freshwater and analytical research. Cawthron is leading the programme, headed by Kevin Heasman and funded by the Ministry of Business, Innovation and Employment, to advance open ocean shellfish aquaculture.

For centuries around the world, people have farmed mussels and shellfish in sheltered sites inshore, using long lines anchored to the seabed and kept afloat by a series of buoys that dangle droppers, or ropes, into the water. For mussel farming, the droppers are seeded with spat (baby mussels), which are then on-grown to harvest. Other types of shellfish such as oysters are also farmed using mesh bags or trays.

The challenge is that consented inshore sheltered water for farming is very difficult to get, yet the world’s seafood demand continues to increase. Finding innovative ways to facilitate efficient and sustainable aquaculture in the open ocean is therefore becoming an ever-growing need.

Professor Alexander says harvesting offshore also presents a number of specific challenges.

“These include boat traffic and larger waves, which might cause the mussels to get knocked off the dropper ropes because of the greater movement of the buoys at the water surface. So, the big issue is, if you are going to farm shellfish out in the ocean, how can you do it efficiently and sustainably?”

While the team is not at liberty to discuss some of the solutions it is looking into, Dr Alexander says there are a variety of ways to improve on the current high-maintenance technology, which is primarily surface-based but static.

“The project team are asking questions like, ‘Can you put the farming systems below the surface?’ This is one of the main ideas that has been floating around for a while. But then how do you access them for maintenance and harvesting? How do you know if the spat ropes below the surface are getting overloaded? Then, what do you do about it?”

One of the key issues is the ability to monitor the farms to ensure they are not being overloaded and that farmers don’t miss the optimal window for harvesting. With the new system being offshore, and potentially below the surface, finding an efficient method for keeping tabs on the farming system is more difficult.

“If you are harvesting offshore, the system is obviously not close by, so you would have to take a boat out to the farm, but it can’t be just any boat. It would have to be a fairly large boat and one with the capability to travel 8 to 15 kilometres offshore in conditions that can be pretty rough,” says Professor Alexander.

But with these challenges comes opportunity. Cawthron Institute, with the help of Professor Alexander and his team, could discover a technology and process that are more economical than the current way of growing and harvesting mussels and shellfish and therefore ensuring the security of seafood supply in future.

Professor Alexander believes modern information and technology can revolutionise shellfish farming by making it more efficient.

UC PhD student Sam Godsiff has been integral to the project because of his family history. He grew up farming mussels in Aotearoa New Zealand with his father and has provided crucial insight into the intricacies of the current process.

“He brings a lot of background and hands-on experience to the table that some of us don’t have,” says Professor Alexander.

The team at UC is an integral part of the Cawthron-led project, which also includes scientists based offshore. There is significant international interest from Europe, the United States of America and China as this new technology could also facilitate their own production of species. Some of the team designs that Professor Alexander and Mr Godsiff contributed to are now in the process of being produced for trials.

MIL OSI