Origin of Ninety Mile Beach Mussel Spat Finally Revealed

Origin of Ninety Mile Beach Mussel Spat Finally Revealed

Mussel spat collection on Te Oneroa-a-Tōhe/Ninety Mile Beach is a regular occurrence, with spat going to most mussel farms in the country.

It’s a $380 million a year industry.

But most mussels from New Zealand aquaculture farms come from spat collected at Te Oneroa-a-Tōhe/Ninety Mile Beach, which in turn came from other sites in Northland, according to new research.

The mussels that fuel Aotearoa’s lucrative aquaculture industry come from reefs around Te Oneroa-a-Tōhe/Ninety Mile Beach, according to Project Moana scientists who have just published their findings after three years of research.

Mussel spat collectors are regularly spotted on the beach harvesting tons of seaweed containing the spat for resale to aquaculture farms, where it is cultured and then sold. Until now, it was unclear where the spat came from before it washed up on the beach.

“New Zealand’s green-lipped mussel aquaculture industry is worth $380 million a year. The industry is largely dependent on wild-caught baby mussels, known as spat, which wash up attached to seaweed on Te Oneroa-a-Tōhe/Ninety Mile Beach. Until now, we had not identified the source of the spat, and this posed a threat to the aquaculture industry that depends on it,” said Dr. Romain Chaput, a postdoctoral fellow at the University of Victoria who led part of research.

Moana Science lead oceanographer Dr Joao de Souza of MetOcean Solutions said it was important to know the source of the spat.

“Knowing where the mussel beds are, agencies can work with hapū and iwi to establish a protection regime that will benefit everyone,” de Souza said.

Chaput said the mussels spend up to six weeks as larvae, which means they can be transported hundreds of miles before landing on the beach.

“In Project Moana, we used ocean modeling and genetic analysis to determine the source of spat that land on Te Oneroa-a-Tōhe/Ninety Mile Beach,” he said.

Ocean modeling and genetic studies show spat that wash up on Ninety Mile Beach come from nearby mussel reefs - particularly those off Ahipara, Tiriparepa/Scott Point and Hokianga.
Ocean modeling and genetic studies show spat that wash up on Ninety Mile Beach come from nearby mussel reefs – particularly those off Ahipara, Tiriparepa/Scott Point and Hokianga.

“The genetics of the mussels show that the spat landed on Ninety Mile Beach come from nearby reefs. Spat from the area are genetically similar, but markedly different from mussels from other parts of Aotearoa.

Chaput said this is supported by ocean modeling done by Project Moana.

“By tracking particles in ocean hydrodynamic models, we found that spat landing on Te Oneroa-a-Tōhe/Ninety Mile Beach is most likely to come from mussel reefs off Ahipara and, to a lesser measure, from Tiriparepa/Scott Point and Hokianga.

“Research shows that although mussel larvae could theoretically be carried hundreds of miles out to sea during their month-long journey, we now know that off the west coast of Northland they are not at all transported very far – the spat come from local mussel beds..”

Kevin Oldham, chair of the Marine Farming Association’s R&D committee, said knowing the location of mussel beds that the aquaculture industry relies on for seed allows resource managers and communities to protect them for generations. future.

Most green lipped mussels from New Zealand aquaculture farms come from spat that wash up on Ninety Mile Beach
Most green lipped mussels from New Zealand aquaculture farms come from spat that wash up on Ninety Mile Beach

Green-lipped mussel facts:

■ Green-lipped mussels) are native to New Zealand and have a moderately complex life cycle.

■ In the wild, they can live for several years and reach 20 cm or more (shell length), but most have become active breeders by the time they reach 4-5 cm.

■ Adults release their gametes into open water. Eggs, sperm and later larval stages are planktonic. They will drift in the sea for about three to four weeks before they can settle.

■ Newly settled individuals (spat) are small (0.3 to 1 mm shell length). Even after initial settlement, they remain able to re-enter the gallery until they reach a shell length of about 6 mm (about one month after initial settlement).

■ In the wild, they tend to first settle on fibrous materials (algae and seagrass, etc.) in shallow/intertidal waters, then actively re-enter the drift before finally settling on firmer substrates (rocky and biogenic reefs, often in deeper water).

■ Cultivated mussels are cultivated on so-called longline systems. Each longline system consists of a “backbone” stretched over a line of surface floats and anchored to the seabed at each end.

■ On the surface of the sea, the backbone generally extends over about 110 m and carries “dropper ropes”. The cultured mussels are seeded onto the dropper, which hangs from the spine in a series of loops. Depending on water depth, each loop can extend up to approximately 20m.

■ A backbone can carry approximately 2.5 to 3.5 km of droppers in total.

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