Joys in store for mussel fans

A mussel breeding project in Nelson could double harvest sizes and give consumers choice of mussels as varied as a wine list.

The $2 million Cawthron Institute project is building a catalogue of captive bred mussel 'families', that will break farmers' reliance on the wild variety.

Research scientist Rodney Roberts says the concept of selective breeding is long overdue.

"At the moment we farm just one type of wild mussel and we don't have the chardonnays or the sauvignon blancs."

He said there was a misconception the project was trying to breed a super mussel.

"It's not about that at all. It's about having a whole raft of choices with known characteristics that companies can pick and choose from."

He said eventually there could be a catalogue of more than 100 'families' with distinct characteristics.

These could include colour, females are pink fleshed whereas males are white, chemical composition and growth rate.

Roberts said new company might be set up, after the project was completed, to manage the catalogue and supply mussel brood stock.

Farmers would then spawn the spat and grow them in pond nurseries before transferring them to the sea on growing ropes.

The biggest challenge with captive breeding was getting consistency during the larval period when the mussels could swim.

"It's hard just keeping them alive, let alone growing and healthy," Roberts said.

Baby mussels, called spat, are currently farmed wild from Ninety Mile Beach where they wash up on the shore attached to seaweed.

The spat are placed inside bio-degradable stockings wrapped around ropes, for them to attach to, and put back into the sea until they mature.

Getting wild spat to attach to ropes is extremely difficult. The loss rate is 95 per cent.

A farm trial to rear Cawthron bred spat and attach them to ropes must reduce losses to 40 per cent to ensure the commercial viability of the project.

However, preventing spat loss is not as simple as closing the farm gate.

Mussel spats can cut themselves free in order to drift or crawl away in search of fresh pastures.

The trick is convincing them to stay put.

"It's a critical step in getting from the hatchery to the sea. What we call the nursery phase," Roberts said.

Nelson based Aotearoa Seafood is building 3ha of ponds for the nursery stage trial.

If this is successful a further 17ha will follow to create a full commercial venture.

Operating at full capacity, the ponds would produce millions of spat every year.

Chief executive Keith Palmer anticipates building and testing the mechanics of the aquatic kindergarten will take 18 months before the trial proper can begin.

Growing the captive-bred spat to a larger size before attachment to growing ropes will reduce the risk of loss.

Palmer said captive bred spat about 5mm long would be needed, which is up to 10 times larger than wild spat.

Palmer has three targets. Uniformity of mussel size, six-month reduction in growing time and eliminating closure due to the spawning cycle.

Only 50 per cent of the present mussel harvest is of the consistent size and quality demanded by customers.

Those that are either too big or small are sold at a discount.

The aim of selective breeding is to produce consistent medium-sized mussels that sell at a premium price. In theory the premium harvest could be doubled.

The spawning cycle forces a two-month closure each year.

Palmer said the project aimed to raise an asexual mussel, which would allow year-round farming.

The controlled pond environment also reduces the risk of infection from the poisonous algae blooms that paralysed the industry four years ago.

These potential benefits would provide greater stability for a $150 million industry that exports 95 per cent of its harvest.

The research is especially important in light of a Herald report last week that detailed a marketing assault on United States restaurant chains by the NZ Mussel Industry Council.

The breeding project, half funded by a Technology for Business Growth grant, is expected to be finished within three years.

DESIGNER MUSSELS

* A $2 million breeding project aims to create 100 distinct styles of mussel.

* Selective breeding is common-place in agriculture but is a new trend in aquaculture.

* Green shell mussel exports were worth $133 million in 2003.

* Total seafood exports were worth $1.06 billion.

Source: SeaFIC, Statistics New Zealand.