Hopes of seeing a mangrove mowing hovercraft in action about Tauranga Harbour are being delayed until March 2015.

Mangrove mower. Photo: supplied.

Originally the Bay of Plenty Regional Council hoped to have the first of its kind hovering mangrove mower in action before Christmas.

Manufacturing delays and the start of the bird nesting season means the latest step in the council's ongoing mangrove management scheme will not be able to show its worth until next year.

'They still completing construction and getting the engine fitted at the moment, we will be starting trials in March,” says BOPRC general manager environmental delivery Warwick Murray.

The Christchurch-based subcontractor building the hull experienced delays getting some equipment, which put the whole project behind.

'We could have done it but we really wanted to make sure. I didn't want to overly rush the construction so we have got, so that we have got everything right,” says Warwick.

'So I agreed to put it off until after the nesting season,” says Warwick.

'The company that's doing it is in Auckland, but had a subcontractor in Christchurch to build the hull. We are lined up for March hopefully.”

The regional council is having the hovering mower built because of it's really light footprint, meaning it won't be crushing the other mudflat communities.

'It will leave no footprint, have negligible effect on the benthic community and also has some advantages in it can move between estuaries, cover ground more readily, move a bit faster so operating costs will be less,” says Warwick.

'It's still unproven as a technique, so we are trying to be innovative trying adaptive ways of dealing with this, but it's a pretty exciting possibility really.”

The hovercraft, with mower blades attached, is intended to prevent the further encroachment of mangroves by cutting down mangrove seedlings. It is not intended to tackle mature growth.

'Basically, it's going to have exposed mower blades out front. All it needs to do is nick off the head of the mangrove seedling. Once you take the leaves off, then it won't grow again,” says Warwick.

'It's a bit like a Flymo [a New Zealand designed hovering lawnmover popular in the 1980s], but with the blades on the outside.”

Mangroves in Tauranga Harbour have expanded exponentially during the last 50 years, and there are now more than 900 hectares of mangroves fringing the waterfront.

The expansion is blamed on increased levels of sedimentation in the harbour and a reduction in the frequency of hard frosts.

Mangroves spread via propagules, germinated seed pods, from mature plants which are dispersed by tides and currents to establish in open, sandy flat areas.

The more mangrove plants there are, the more mangrove propogules are produced – and the faster the mangroves spread.

The hovercraft is expected to mow about 600 hectares of seedlings annually, while causing minimal environmental damage.