Floating dock used to stifle marine pest invasion
A new tool in the fight against marine invaders in the top of the south was deployed for the first time at Nelson yesterday.
Acquired by the Nelson, Marlborough and Tasman District Councils in conjunction with the Ministry for Primary Industries, the floating Fabdock will allow vessels of up to 20m to be treated for harmful marine organisms growing on their hulls.
Marine Biosecurity Partnership co-ordinator Peter Lawless said hull fouling accounted for 90 per cent of the risk in the spread of invasive marine organisms around New Zealand.
Most of this risk was on recreational vessels and the new dock would be able to treat vessels in emergency situations around the top of the south.
‘‘This year we have found marine pests on Nelson boats as far afield as Queen Charlotte Sound so there is still work to be done on getting the clean below, good to go message out.’’
The new dock can be transported to the vessel on a trailer and be deployed on site. The dock is inflated where it is needed. It was built by Taumarunui-based manufacturer Incept Marine for this purpose, just like an inflatable boat.
‘‘People haven’t always been able to get on the Nelson hardstand or something’s arrived and we just need to deal with it, particularly for the remote locations in the Sounds – you don’t want to move those boats around.’’
The floating docks have been used in Northland for the last two years and more recently in Southland where the spread of Japanese seaweed wakame has caused issues throughout Fiordland.
In the top of the south, the acquisition of the Fabdock was triggered by the local management plan to combat Mediterranean fanworm, which Lawless said was a threat to mussel farms in the region.
The pest could grow to more than 600 millimetres in length and could starve native marine species of food and living space.
The fanworm had been already confirmed in Tarakohe, Nelson and Picton and had so far been kept in check by diver removal in those locations.
Risk vessels can be found far from the ports where they can be hauled out and organisms can drop off in transit.
Lawless said there had been a case as recently as late last year of a fanworm-contaminated vessel moored by the Boulder Bank undetected for 12 months.
‘‘All the vessels coming into the marinas we are keeping an eye on that but the ones that go on private moorings we don’t necessarily get any information on it – luckily it hadn’t reproduced so we dodged a bullet on that occasion.’’
The dock will be based in Nelson at the NZ Underwater Services yard.
With the help of Nelson Rowing Club and Nelson harbour master Dave Duncan, trials were being held yesterday at Port Nelson to decide how best to store the 300kg device.
‘‘We want it mobile so they’ll make a decision whether they’ll get a specially-made trailer for it or whether its easier to go on a pallet and put it on a truck,’’ Lawless said.
Chlorine bleach is used to kill the pest organisms once the boat has entered the dock and it is sealed.
Lawless said tests undertaken by Cawthron Institute showed that organisms could be killed within about an hour and a half using the chlorine method – while an alternative treatment for vessels larger than 20m was to wrap them in plastic.
‘‘The chlorine is neutralised before the dock is opened to the sea again. It’s not a magic bullet but a valuable addition to the toolkit.
‘‘The most important thing is for boaties to keep their antifouling up to date.’’