Aquaculture trial aims to solve problem of runaway mussel floats

Regular floats in Marlborough.
Regular floats in Marlborough. Photo credit: Supplied / MPI

It is hoped a new research trial by a Tasman-based aquaculture company will lead to fewer mussel floats being lost at sea, saving the industry money and leading to less plastic in the ocean.

The research will test an improved mussel float - made by aquaculture float specialists SS Floats  - which is designed to withstand conditions in rougher open waters.

"Mussel farming in New Zealand began in sheltered bays in the Marlborough Sounds, so the old design, which has been used for the past 40 years, worked pretty well," says Paul Smith, lead designer for SS Floats. 

"However, the industry's move to more exposed waters has driven our need to come up with a new design."

Current floats are made of plastic and occasionally come loose in adverse weather or tidal conditions.

According to the Ministry for Primary Industries (MPI), data collected over the last 10 years shows between 500 and 1500 floats are lost from the Top of the South mussel farms each year, with an annual cost of at least $500,000.

Ned Wells, general manager of the Marine Farming Association, which is supporting the research project, says floats that get loose are generally recovered.

"Despite that, it's an expensive exercise for companies to go round and collect them."

Smith hopes his company's prototype will help reduce the number of runaway floats, and in turn avoid unwanted recovery costs for the industry. 

The new design is already being tested in local waters.
The new design is already being tested in local waters. Photo credit: Supplied / MPI

"Appropriate buoyancy is a critical element of longline mussel aquaculture and requires a delicate balance," he says.

"Too much flotation and crops are shaken by wave energy at the surface; too little flotation and lines can sink. Both can result in crop loss."

He says floats are already being tested in local waters and performing well.

"We now need to test them in different parts of the country with more exposed waters."

The project has received $72,500 towards its total costs of $145,000 from MPI's Sustainable Food & Fibre Futures fund.

Testing of the floats will take place in open waters in Golden Bay, Tasman Bay, Pegasus Bay and off the coast of Coromandel.

"If this project is successful it will mean one less source of plastic in our marine environment," says Steve Penno, director of investment programmes at MPI. 

"This could help the mussel industry with another step towards boosting its sustainability, while saving time and money."