New Zealand / Environment

Marlborough Sounds' marine life improving after mussels project - researchers

14:15 pm on 28 December 2021

A mussels project being trialled in a part of the Marlborough Sounds is already helping boost the area's marine life, researchers say.

NIWA and University of Auckland PhD student Trevyn Toone deploying harvested mussels in Pelorus Sound. Photo: NIWA/Rebekah Parsons-King

Researchers have been working with local marine farmers, iwi, and the Ministry for Primary Industries to place green-lipped mussels back in their natural habitat on the ocean floor.

It is thought that some places in the Sounds have had a 97 percent decrease in wild mussels since commercial fishing began.

Auckland University and Niwa researchers are hoping to turn this around with the three-year project, which is led by Trevyn Toone and Emilee Benjamin.

Toone said the project not only enhanced the natural environment, but helped cut down on waste.

"Often mussel farmers have extra mussels that they haven't been able to sell or that for some reason aren't ideal so it would be really nice if these farmers can then go out and take those mussels and actually restore them into the wild, instead of having them go to waste," he said.

The mussels filtered the water and attracted other sea creatures, he said.

Benjamin said the change in the aquatic life after mussels were placed was almost immediate.

"We've seen an increase in blue cod, and increase in macro algae and sea cucumbers and a bunch of other animals, including triple fins, that have made the beds their home," she said.

"And we see that [happen] almost the moment we put the mussels down."

Green-lipped mussel. Photo: NIWA/Rebekah Parsons-King

The project is currently only operated in Pelorus Sound, but has plots in lots of different environments.

"[We] restore mussels really all over. Sometimes they're in a tidal area, so on the next low tide, we can just go out to some of these restored beds, count how many mussels are alive there, how many are dead - sort of just see how well they're doing," Toone said.

"But for some of our deeper restored reefs, we really have to scuba dive down there."

So far, 60 tonnes of mussels have been placed.

Toone and Benjamin would like to see the programme extended beyond its three-year trial (which is set to conclude next year) and would like to see it taken to other parts of the Sounds.

NIWA divers working in the Marlborough Sounds on the mussel restoration. Photo: NIWA/Lana Young

Both said it had been a collaborative project that would not have happened without the local community's support.

"We've had a huge amount of help from the marine farmers that have really made this project possible. They've provided so much in kind support, whether that's the use of their boats or mussels and everything," Emilee said.

"Literally none of it would be possible without their help."

Toone said it was the farmers who first brought up the issue, after seeing the decline in wild mussels for many years.

The overall aspiration of the project is to make marine farming regenerative and have marine farmers placing their own surplus mussels into approved areas as part of their regular work.