Farming oysters in the open ocean: New technologies on trial in Ōpōtiki   

29 June 2023

Open ocean oyster farming is one step closer to becoming commercially viable thanks to a new trial as part of a national open ocean aquaculture research programme. Cawthron Institute researchers are leading the five-year MBIE-funded Ngā Punga o te Moana research programme. They are collaborating on this trial with Moana New Zealand, Stainless Concepts and Whakatōhea Mussels Ltd who have deployed the new trial structures on their marine farm off the coast of Ōpōtiki.

Programme leader Dr Kevin Heasman says open ocean farming will be necessary to support the growth of Aotearoa New Zealand’s aquaculture industry ambitions and its resilience in the face of increasing environmental pressures, including climate change.

“As waters warm and the farming space available in-shore fills up, we’ll need to  extend further off-shore and this will require new methods of farming and new technologies.”

Heasman says that Whakatōhea Mussels are the only company commercially growing mussels offshore in Aotearoa New Zealand, and there is no one currently farming oysters in this high energy environment.

“Essentially we classify open ocean farming as any marine location where the farm will be exposed to high wind and waves and strong currents – it’s not so much about the distance offshore as it is about the level of energy at the site.”

The current trial involves experimentation with new structures that have been specifically designed to withstand these conditions.

“Our new structures, known as subunits contain our oysters. The site where they are growing is 11km from the coast and 50m deep where the oysters are suspended at about 9m below the surface to avoid surface wave energy .”

Heasman says the preliminary results are promising.

“We deployed 8000 spat just over a month ago, and their growth rate in that time has been good with one sleeve weighing nearly 10x its original weight.

“There was some minor fouling on the sleeves, but not enough to restrict waterflow to the oysters, and the oysters were clean with no mortalities.”

Heasman says the next check-up on the oysters will need to be brought forward due to their fast growth rate, at which point the oysters will be graded and split into smaller stocking densities for the remainder of the trial.

“There are a lot variables we’re considering and with Industry input we’ll be further developing methods and equipment to adapt to the high energy environment. At this stage we’re confident the approach is a good one and we’re planning further trials to overlap with this one so that we can test and refine our technology and methods.” 

“A core goal of the Ngā Punga o te Moana research programme is to develop the technology and methodology required for commercial open ocean farming of oysters and other species of shellfish in Aotearoa New Zealand and this is a confidence building step in that direction.”

To read more, check out – Case Study: New open ocean oyster farming technologies on trial


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Credit: Cawthron Institute. The new trial sub-unit being deployed off the coast of Ōpōtiki on industry partners Whakatōhea Mussels’ marine farm.

Kevin Heasman

Kevin Heasman

Aquaculture Scientist - Cawthron Institute

Credit: Cawthron Institute. Sorting spat at the month-1 check in.