Invasive Species

Community Wellbeing
Healthy Ecosystems
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Risks to our Catchment
Freshwater pests in the Otago Region include waterweeds like lagarosiphon, pest fish, and invasive alga like didymo, lindavia (lake snow) and cyanobacteria. These introduced species cause enormous damage to our unique freshwater habitats and diminish our recreational opportunities.

Aquatic pests can also have adverse economic impacts including clogging dams and drains, and reducing suitable habitat for eel and whitebait. Once freshwater pests become established, they are difficult and costly to control. If we can prevent them getting into our waterways in the first place we have a better chance at stopping their spread.

One of the most visible and well knows pest plants in Lake Wānaka is Lagarosiphon.

Click here to see what lies beneath the surface of our lakes and rivers.
Watch this video by Wanaka MAC student about Lagarosiphon.
NIWA video: Diving deep to check up on our lakes.

Lagarosiphon and other invasive pests have had a devastating impact on our lakes and how we can use them. These pests are primarily spread by human activities, such as accidental transfer through boating and fishing gear contaminated with plant fragments. Pieces of plant as small as 1 cm have the potential to start a new infestation. Lagarosiphon has been managed in Lake Wanaka since 1974 to help protect the lake and other pristine and iconic lakes in the Otago region.

The importance of “CHECK, CLEAN, DRY”

“If it’s wet, it’s a threat.” Did you know many aquatic pests, such as didymo (alga that causes rock snot) and lindavia (alga that causes lake snow) can survive for months out of water in moist environments? This is why utilising the ‘CHECK, CLEAN, DRY’ method is so important in stopping the spread of these freshwater invaders. 

We may not have the ability to turn back the clock and stop aquatic pests from first entering our lakes and rivers, but we can come together as a community to stop their ongoing spread. The simple ‘Check, Clean, Dry’ method can reduce the spread of aquatic pests, such as lagarosiphon, into new areas. Remember to:

  • Check that your vessel and equipment are free of aquatic pests.
  • Clean equipment using 10% dishwashing detergent mixed with water and leave item wet for 10 minutes.
  • Dry your gear thoroughly (recommended time is 48 hours) before moving between waterways.

For more information on CHECK, CLEAN, DRY you can visit: Ko Tātou This Is Us | Biosecurity – Keep NZ safe from pests and diseases

Wetsuit hanging out to dry to remove aquatic pests.

Get involved

You can help stop the spread. Protect our waters from freshwater pests.

  • Drainage and machinery contractor – ensure any weed is removed from machinery before moving to other water-bodies and waterways.
  • Fisherman or eeler – remove all fragments of weed from nets, fishing equipment and waders before you leave the area. Salt bath and/or bleach fishing nets.
  • Boat operator – check boats, motors, trailers and anchor lockers for tag-along weeds immediately on removal of equipment from the water.
  • Aquarium owner – don’t dispose of aquarium contents into or near a waterway.
  • Tramper and hunter – check dogs, boots and boats for weed before you leave the area.
  • Landowner – don’t allow drainage equipment, eel nets or boats into water bodies on your property unless they are free of weeds.

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