Stopping the spread of aquatic pests

Lagrosiphon entangled on a boat motor.

Lagrosiphon entangled on a boat motor.

New Zealand has some of the most beautiful lakes and rivers in the world but we need to stop the spread of freshwater pests so that our waterways stay that way.


It only takes one pair of tramping boots, or a wet lifejacket to give a hitchhiking freshwater pest a ride to a new location, where it can establish and cause damage. And once there, the detrimental effect the pests can have can diminish the quality of our recreational experience.

Freshwater pests like didymo for instance, spoil river activities for people and they also have the potential to affect the habitats of freshwater plants and animals.


Currently, the South Island is a controlled area for didymo, which makes it a legal requirement to clean all gear used in the water before going from one waterway to another. To date, no didymo has been found in the North Island, which is why it’s doubly important to check, clean and dry all equipment (including boots and boats) before moving between waterways.


The Ministry of Primary Industries has an active campaign in place, which focuses on people likely to travel between waterways – especially kayakers, canoeists, jet boaters, pleasure boaters, anglers and fly-fishers. Trampers, hunters, swimmers and drivers of campervans and off-road vehicles are also included. The campaign is supported by a network of partners including the Department of Conservation, regional councils, Fish & Game New Zealand, iwi and affected industries.


Lagarosiphon major.

Lagarosiphon major.

Closer to home, Environment Canterbury is implementing a Check Clean Dry programme within the Canterbury region.


“It’s about encouraging people to prevent aquatic weed spread by checking their gear, cleaning it and if cleaning is not feasible, then drying it,” says Graham Sullivan, Regional Manager, Environment Canterbury.


“There are a number of aquatic pests, including those that affect water margins, that are, or could be, of significance to Te Waihora and its tributary streams and drains,” he says.


These include purple loosestrife -Environment Canterbury and the Department of Conservation are currently working on its control in the Tai Tapu area. Beggars Tick is also subject to control measures by Environment Canterbury; and plants like Carex pendula, reed canary grass, and phragmites are on the watch list.


Waterweed on propeller. All photos courtesy of NIWA.

Waterweed on propeller. All photos courtesy of NIWA.

“Lagarosiphon, egeria and hornwort could also be an issue if they got established in the Te Waihora catchment and we focus on these three species in our Regional Check Clean Dry campaign,” says Graham.


Graham adds that there are a number of measures people can employ to reduce the risk of freshwater pests.


“Even if you don’t know if a pest is present in a waterway, just by checking and taking debris off your equipment and cleaning it with soapy water before moving to another waterway can stop unknown pests moving about – fish eggs included.”


If you think you have seen an unusual plant or aquatic animal in a waterway let us know.  You can contact a biosecurity officer through Environment Canterbury Customer Services on  0800 EC INFO.



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