Strategies and success against invasive aquatic plants

Strategies and success against invasive aquatic plants Strategies and success against invasive aquatic plants Strategies and success against invasive aquatic plants Strategies and success against invasive aquatic plants

The words 'predator-free' and 'pest-control' usually bring to mind animals like possums and rodents; but for New Zealand lakes and rivers, biosecurity threats are more likely to involve weeds and plants.

In Southland, Boffa Miskell ecologists and biosecurity experts have been working alongside Land Information New Zealand (LINZ) and the National Institute of Water and Atmospheric Research (NIWA) on the forefront of the battle against Lagarosiphon major, and significant gains have been made.

A recent report from LINZ shows large parts of Lake Wanaka remain free of the invasive weed, and monitoring by NIWA researchers confirmed the success of these efforts.

Under the direction of project manager Marcus Girvan, from the Boffa Miskell Christchurch office, divers pulled more than 600 catch-bags of weeds from the  lake over the last year, and lined more than 20,000 square metres of the lake bed with hessian matting, to starve the weed of sunlight.

Lagarosiphon grows up to a metre a month and at its full height can reach five metres. As well as choking out native aquatic plants, the weed can cause problems for boat users and swimmers close to shore.

Since 2009, Boffa Miskell has been managing biosecurity operations on LINZ’s unalienated Crown land (riverbed and lakebeds) and in 2014, formed a strategic partnership with LINZ, with the aim of focussing on innovative solutions to achieve the biosecurity programme goals.

On the North Island, our Hamilton office hosted a New Zealand Coastal Society regional event. Representatives from the Northland Regional Council (NRC) explained how they are taking action in managing the threat presented by marine pests.

For Northland, the biggest concern is the spread of fanworm (Sabella spallanzanii), which first appeared in New Zealand in 2010.

Fanworm’s presence in an area can alter water flows and sedimentation, and fanworm competes with native filter-feeding species and with farmed bivalve molluscs (oysters and mussles) for food.

Sophia Clark (Biosecurity Manager – Marine & Strategy) and Justin Murfitt (RMA Planning and Policy Manager) explained the NRC strategy for managing marine pests like fanworm by using a three-pronged approach involving legislation under the RMA and Biosecurity Act.

Boffa Miskell marine ecologists Jacqui Bell and Sharon De Luca attended, along with around 30 guests from a variety of disciplines including scientists from Waikato University and NIWA, planners from DOC and Regional Councils, and local marine farmers. The talk generated a lot of interest in the current marine pest management initiatives, and  opportunities for improved collaboration and inter-regional engagement.

(Photos of Lagarosiphon major and Elodea canadensis: RohanWells/NIWA)

For further information please contact Dr. Jacqui Bell, Dr. Sharon De Luca or Marcus Girvan

4 May 2018