Freshwater biosecurity

You can help to protect your favourite Taranaki waterways if you always check, clean then dry all gear when moving between waterways.

Freshwater pests, including exotic plants, algae and fish, can seriously harm environmental, aesthetic and recreational values of Taranaki’s rivers, lakes and streams.  Pests can be spread by plant fragments trailing on equipment and inadvertent (or intentional/illegal) movement of fish, aquarium plants and algae. Even a single drop of water from a boat bilge can contain algal cells capable of expanding rapidly in the environment, such as didymo or lake snow. 


Check and chuck – take off any bits of weed you can see on your gear

Remove any plant matter from your gear and leave it at the river or lake bank or put it in the rubbish. Don't wash plant material down any drain.


Clean with a detergent mix, because if you use just cold water you are keeping these weeds and pests alive

Clean any gear that has been in contact with the water, including boots, fishing gear, your boat or trailer.

Use a mix of 10% dishwashing detergent or 2% bleach with water, or use hot water. See the MPI website for more detail about cleaning options for your gear.(external link)

Carefully check areas where freshwater pests could hide, such as jet units, bilge pumps, outboard motor cooling systems, anchor recesses, wheel arches and trailers.


Dry your gear, if you can, because moisture helps these weeds and pests survive

Make sure your gear is completely dry to touch, inside and out, then leave it dry for at least another 48 hours before you use it. Didymo, for example, can survive for months on moist gear.

The Taranaki Regional Council is working alongside the Ministry of Primary Industries and the Department of Conservation to promote the ‘Check, Clean, Dry’(external link) campaign.  

Why is it worth the effort?

A number of plant and fish species represent a real threat to native ecosystems here in Taranaki. Here are some of particular concern:


HornwortHornwort poses a serious risk to Taranaki lakes due to its ability to rapidly invade freshwater habitats, crowding out native species, impeding drainage, flow boating access and fishing lines.

Within Taranaki, Hornwort is currently present in three lakes - Lake Rotorangi, Lake Herengawe and Lake Mangawhio. There are concerns it could spread further within the region, infesting other Taranaki lakes and waterways. The Council is working with Te Kaahui o Rauru Haapori(external link) and other agencies to prevent this but need the public's help.

More information (Weedbusters website)(external link)



DidymoDidymo is an invasive and unsightly (cotton wool-like) algae that completely smothers the rocky substrate of pristine rivers and streams. This has severe impacts on ecosystems health and fisheries.

Didymo is currently widespread through the South Island, but is not yet present in the North Island. Help us to keep it out of our Taranaki waterways.

More information (Biosecurity NZ website)(external link)



Lake snow

Lake snowLake Snow (Lindavia intermedia) is a relatively new freshwater pest. The invasive diatom species can cause algal blooms called lake snow.

Lake snow mucus can clog water intake filters, boat hulls, fishing and other recreational equipment.

Lindavia intermedia has now been found in multiple regions in both the North Island and South Island but is yet to be confirmed in Taranaki.

More information (Otago Regional Council website)(external link)

Oxygen weed/pond weed

Oxygen weed/pond weed (Lagarosyphon, Egeria and Elodea) have similar characteristics and are present in various Taranaki waterways and lakes.

If transferred to a new waterbody they can spread rapidly. Controlling them, let alone eradicating them, is extremely difficult.

Lagarosiphon(external link) | Egeria(external link) | Elodea(external link)  - Weedbusters website

Other aquatic plants

Salvinia/kariba weedMany other exotic plants that may impact upon our waterways. If you have suspicions about any unknown species you encounter, please contact the Council’s Environment Services section.

Of particular concern is the highly invasive Salvinia (kariba weed). It is currently in the Waikato but not in Taranaki. However, it could be transported by freshwater users or possibly by sea currents.

Salvinia /kariba weed (Weedbusters)(external link)

Pest fish

Taranaki has comparatively few pest fish species, when compared with neighbouring Waikato and Manawatu regions. There are, however, small and localised populations of gambusia (mosquito fish) and rudd. A few small populations of koi carp have historically been eradicated from small ponds. Red-fin perch, actually a regulated sports fish, is a species that is widespread in Taranaki and is a voracious predator of native aquatic species.


Gambusia (mosquito fish)


Brown bullhead catfish.

Pest fish may prey on native fauna and trout. Some species are herbivorous, grazing on native aquatic plants and rooting about in muddy substrate making water turbid and mobilising nutrients unnaturally in the water column.

The risk of new pest fish becoming established in Taranaki is ever-present, given that they already in neighbouring regions. In particular brown bullhead catfish, koi carp and tench are species that we do not want to establish in Taranaki. If you are boating or fishing outside of Taranaki, please Check, Clean, Dry to avoid inadvertently bringing young fish or eggs back to Taranaki waterways.

Advice for specific freshwater user groups

Select the relevent category/ies:

Boaties (including kayakers and waka crew)

Ensure you Check, Clean, Dry all wetted surfaces, internal and external. Pay special attention to pumps and bilges, equipment wells, matting, motors and trailers. Boat ramps can be high-risk areas for aquatic weeds, so ensure you check trailers too.

Anglers and whitebaiters

Pay special attention to waders (no felt soles), nets, wet clothing, buckets and fish bags.

Mountain bikers, 4WD drivers and other incidental users

Check, Clean, Dry applies to you, too, if you're moving across and between waterways. Focus on wheels, wheel arches, and undercarriage.

Aquarium retailers and owners

Do not sell or distribute aquatic plants that feature in the National Pest Plant Accord(external link). It is illegal to dispose of or release any aquatic biota (either native or exotic) into a New Zealand waterway (including stormwater drains) without the appropriate permissions.

Freshwater event organisers

If your sports club or organisation is hosting an event in Taranaki whose participants may bring freshwater-related equipment into the region, or involving movement between waterways within Taranaki, please contact the Council for advice and support on how to promote and deliver Check, Clean, Dry measures.