Challenges in mussel farming
Transcript
Unpredictable spat supply
Professor Andrew Jeffs (Leigh Marine Laboratory) describes the unpredictable nature of the spat supply from Ninety Mile Beach.
Transcript
Professor Andrew Jeffs
The spat fall on Ninety Mile Beach is quite unpredictable. There’s a general pattern – it generally turns up between August and the end of December and sometimes a secondary supply in January, February, March, but it varies from year to year, and the volume varies enormously.
Also the quality varies enormously as well. Sometimes the seed mussels that come in are well fed, and once they’re put on the farm, they grow very quickly. Other times, they’re in poor condition, and a large proportion of them die or they get eaten or they swim off before they have a chance to grow up.
The spat fall is absolutely critical to the industry. We’ve got an over $200 million industry that relies on that wild seed supply, and so having a continual supply of spat there arriving is absolutely critical. So there have been periods of almost a year where there’s been no spat available at all and it’s caused a major problem for the mussel industry. And in those times, the industry has shown a huge interest in developing hatchery systems and getting them up and running and trying to produce spat through those alternative methods.
ACKNOWLEDGEMENTS
Sheree Wagener. Professor Andrew Jeffs, Oliver Trottier – Leigh Marine Laboratory, Auckland University. Just the Job, Dave Mason Productions. www.careers.govt.nz/resources/tools-and-activities/just-the-job
Certain photos in this video are the copyrighted property of 123RF Limited, their contributors or licensed partners and are being used with permission under licence. These images and/or photos may not be copied or downloaded without permission from 123RF Limited.
Spat resettlement
Professor Andrew Jeffs (Leigh Marine Laboratory) explains that spat are prone to moving from their original site of settlement and why this can cause problems for mussel farmers.
Transcript
Professor Andrew Jeffs
Mussel spat’s quite unusual from a biological point of view. When they first settle, there’s a swimming seed, which is looking for seaweed to settle on and it settles on the seaweed. If it doesn’t like it, it will actually put out a long thread of snot. Basically mucus which gets caught in the current and then it will let go of the seaweed and then it will use that thread like a parachute to drift off and find somewhere else that’s better for it to set up shop. So if you put mussel seed onto a farm and there isn’t enough food in the water or the mussel was already in poor condition before it got there they’ll quite often put out a parachute and they’ll sail off, sometimes that can take out 90, 95% of your seed mussels.
ACKNOWLEDGEMENTS Professor Andrew Jeffs, Oliver Trottier – Leigh Marine Laboratory, Auckland University.
Predators
Professor Andrew Jeffs (Leigh Marine Laboratory) describes the major predators of New Zealand’s farmed green-lipped mussels.
Transcript
Professor Andrew Jeffs
Mussels are out hanging in the water column, and they’re vulnerable to things coming and eating them.
Probably one of the worst predators for early mussels is fish, especially snapper and spotties – they come and bite, bite and eat the mussels, the baby mussels off the farm. Sometimes you get starfish setting up home on mussel farms, and they’ve got strong arms, and they can pull the mussel shells open and eat the mussels.
ACKNOWLEDGEMENTS Professor Andrew Jeffs, Oliver Trottier – Leigh Marine Laboratory, Auckland University. The Shape of Life. http://creativecommons.org/licenses/by-nc-nd/3.0/
Pea crabs
The New Zealand pea crab is a parasite of green-lipped mussels. Professor Andrew Jeffs (Leigh Marine Laboratory) describes how the pea crab causes problems for mussel farmers.
Transcript
Professor Andrew Jeffs
So it sets up home inside the mussel and starts stealing that food that the mussel’s been gathering so diligently. The pea crab steps in there and grabs the meal before the mussel gets a chance to eat it. So that reduces the productivity of the mussel, and it also causes problems in terms of quality, because the last thing a consumer on the other side of the world who’s paid a lot of money to buy a high-quality farmed mussel from New Zealand wants to do is to bite into a crunchy crab in the middle of their meal.
ACKNOWLEDGEMENTS Professor Andrew Jeffs, Oliver Trottier – Leigh Marine Laboratory, Auckland University.
Toxins
Professor Andrew Jeffs (Leigh Marine Laboratory) explains why mussels are susceptible to accumulating toxins.
Transcript
Professor Andrew Jeffs
There’s a number of types of phytoplankton, those are the tiny floating plants, which produce poisons or toxins. They probably produce them as a way of protecting themselves from fish and what have you from eating them. And so the mussels, because they filter such large numbers of those plants, they accumulate the poisons inside their bodies, and so that accumulated poison then becomes an issue for someone then going and eating a mussel, because there’s a larger volume of poison there which can start to cause problems.
Fouling
Professor Andrew Jeffs (Leigh Marine Laboratory) explains how unwanted organisms can foul mussel lines.
Transcript
Professor Andrew Jeffs
The presence of what we call fouling organisms, things like seaweeds and barnacles and sea squirts, on the mussels when they’re harvested causes quite a bit of a problem, because when they come in, you get a lot of other material mixed in with the mussels. Things like sea squirts in particular start rotting quite quickly and so that has the potential to cause spoilage.
Also the industry has been incredibly innovative and developed systems for opening mussels. And if you have a lot of barnacles on the outside of shells then it causes problems for some of those highly advanced systems for processing mussels.
There’s a machine which uses guided suction cups which sucker onto the outside of the shells and open the mussels. Well, if you’ve got barnacles on there, the suction cups can’t suck because there’s barnacles stuck underneath them.
The other issue with barnacles is our mussels have a beautiful green shell, and if they’re covered in barnacles, they don’t look as inviting as they do when they’re just that beautiful polished green jade colour.
ACKNOWLEDGEMENTS Professor Andrew Jeffs, Oliver Trottier – Leigh Marine Laboratory, Auckland University. Penny White. Happy Aston. NIWA.
