NIWA develops new mussel harvest technology

Researchers at New Zealand's National Institute for Water and Atmospheric Research, NIWA, have developed a machine that measures the strength of mussel shells as part of a three-year study aimed at narrowing down the best time to harvest them and boost returns for shellfish farmers.

The machine is partly based on the same technology used to open and close irrigation gates and uses a linear actuator to apply a compressive force to break the mussel shells, while measuring and recording that force 10,000 times per second.

The multi-million dollar greenshell mussel industry is New Zealand's largest aquaculture export, accounting for $253 million in export income in 2014, and is expected to be an important source of forecast aquaculture industry growth in coming years, mainly through increasing mussel production, supported by a stronger supply of hatchery-bred mussel spat.

NIWA marine ecologist Jeanie Stenton-Dozey said mussels were sometimes less than ideal when harvested and not suitable for the food industry.

"We don't know why in some years mussels lose condition so we have started to investigate how tissue and shell differences relate to fluctuations in their food supply and environment."

Analysis of samples from the Firth of Thames have been taking place at NIWA's Christchurch base since February, assessing seasonal variation in fatty and amino acids along with the sex, shell dimensions, body weight, and strength. The study is being expanded to include Marlborough's Pelorus Sound and Big Glory Bay at Stewart Island to provide geographical variation.

"These data will also provide some insight into the susceptibility of mussels being crushed during harvesting and transport," Stenton-Dozey said.

A mussel hatchery and nursery facility was opened in Nelson earlier this year as part of a seven-year SPATnz Primary Growth Partnership programme established to develop selectively bred, high-value greenshell mussels. The SPATnz PGP programme is co-funded by the Ministry for Primary Industries and seafood processor Sanford [NZX: SAN], which are putting in $13 million each.

Sanford closed its Christchurch-based mussel processing plant in April with the loss of 232 jobs, citing a shortage of natural spat supply. Recent weather patterns have reduced natural spat supply for several seasons and, given the outlook of greenshell mussel crop supply in the short to medium term, the company had combined volumes from its manual opening plant in Christchurch with its automated facility in Havelock.

(BusinessDesk)

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