Check, Clean, Dry to stop freshwater pests

The invasion of freshwater pests into Canterbury's waterways affects us all. If you fish, whitebait, water ski, row, kayak, tramp or just swim, these water weeds can affect your success, safety and enjoyment of our waterways.

Water weeds ruin valuable ecosystems by inhibiting growth of native water plants and reducing likely spawning areas for many types of fish.

Some of the freshwater pest species present in New Zealand, exist within our region, but many of our lakes and rivers remain pest-free.

To help keep it this way, it's important that equipment and vessels are properly cleaned and decontaminated before entering any Canterbury waterway.

Remember high risk species are those that are microscopic. So even if you can't see it, if it's wet, it's a threat!

If you’re enjoying Canterbury Waitaha waterways and believe you may have seen a pest species, check out the pest search. Here, you can identify freshwater, and any other, pest species in the region, and what to do if you see them.

How to prevent freshwater weed invasions


Check boats, trailers and anything else that was in the water, including your dog’s paws if your dog is in the water with you, for any plant material and remove it. Even if the plant appears dry and dead, it may still survive and start a new infestation. Leave debris at the site or, if you find any later, treat and dispose of it in the rubbish. Do not wash down drains.


Wash all equipment (eg, nets, machinery, footwear and clothing) thoroughly with an appropriate decontamination solution (10% detergent or 2% bleach in water) before putting it in any new waterway. 


If you can't clean your gear or animals, restrict use to a single waterway or dry completely to the touch inside and out, and leave to dry for at least another 48 hours.

Particular attention needs to be given to those users who are moving between different waterbodies, catchments, regions and islands with the same vessels and/or equipment.

What else can I do to prevent freshwater weed invasions?

  • Familiarise yourself with the freshwater and marine pests listed in the pest search. That way, if you encounter a pest species while enjoying our waterways, you’ll know what to do to help our control efforts.
  • Do not throw any aquarium or pond material into waterways. Instead, put all unwanted pond material on the garden or compost - your small oxygen weed may become the next threat to native fish, birds and plants.
  • Do not give plants or plant parts away to others until you are sure that they are not a threat to our waterways.
  • Make wise decisions on how to avoid increasing nutrient levels in waterways from fertiliser. High levels of nutrients running into waterways tend to encourage vigorous growth of some weeds.

Guidelines for running a waterway event

If you're running an event in a Canterbury waterway, it's important to tell participants about the need to 'Check, Clean, Dry' equipment:

  • before entering a waterway;
  • before moving between waterbodies;
  • before leaving the area - especially from the South Island*.

This could be a condition of entry on your event registration form. Event signage and cleaning facilities, could also act as a useful reminder.

As the event coordinator, you should also be aware of any freshwater pests that may be present in the area. You can do this by heading to the pest search and toggling the filter for pest type to freshwater or marine.

Each pest has identification information, control instructions, and tips on how to ensure you’re not spreading the pest. For a full list of freshwater species of concern, head to the Pest Search.

Environment Canterbury provide free portable cleaning equipment, which you can book for your event. Contact us on 0800 324 636 or email at to use this or for further biosecurity related advice.

The Ministry of Primary Industries (MPI) also has more information on holding a waterway event.

*The South Island is a controlled area for didymo. This makes it a legal requirement to clean all gear and equipment that has been used in waterways before moving between Islands.
Note: It is an offence under Section 52 of the Biosecurity Act to knowingly transport a pest or unwanted organism to another waterway, and the penalty upon conviction for an individual person, is imprisonment for up to five years and/or a fine of up to $100,000. So be sure to Check, Clean, Dry - everywhere, every time.