Stop clams from spreading

The water we love

The invasive freshwater clam, found in the Waikato River in May 2023, can harm everything we love about the water. It can disrupt our recreation, clog water pipes, and threaten other freshwater species. The clam can only spread if humans move it between lakes and rivers with boats and gear.

How to 'Check Clean Dry'

Check – for what is visible

Remove any visible matter, including any plant material, mud, or clams.

Drain all river or lake water.

Clean – for what is not visible

Blast your gear and craft with tap water, not into a stormwater system or drain (onto grass).

For absorbent materials, use one of these treatments*:

• soak in hot tap water (50 to 55°C) for at least 5 minutes or
• soak in 5% bleach solution (5-litre mix = 250ml bleach in 4.75 litres water) for an hour or
• freeze till solid (overnight) or
• soak in salt solution at 100ppt** (5-litre mix = 500g salt in 5 litres warm water) for 4 hours.

For a full list of Biosecurity New Zealand-approved treatments, including options for situations where none of the above is suitable:

Treatment options for gear made of absorbent material

*Refer to manufacturer’s instructions if needed

** Parts per thousand

Dry – to be sure

Gear: Allow gear to dry to touch, inside and out, then leave it to dry for at least 48 hours (2 days) before using again.

Watercraft: Dry areas inside the watercraft where water has pooled, for example with an old towel, and then leave the craft to dry for at least 48 hours (2 days). The hull of a watercraft will dry when towed.

These new 'Check Clean Dry' steps will also help stop the spread of other freshwater pest species.