Response to Whangamarino avian botulism

This is Waikato Regional Council's response to the cases of avian botulism occurring in the Whangamarino wetland.

Dr Mike Scarsbrook, Waikato Regional Council Science Manager, says:

The Whangamarino wetland is a complex and dynamic system with multiple manmade influences, including land use, flood protection and drainage assets, the Whangamarino weir and hydrodam releases in the upper Waikato River. These all affect natural events in one way or another.

The avian botulism outbreak became evident in January 2023, following a blackwater event which occurred in the Whangamarino and Maramarua Rivers in December 2022. 

A blackwater event occurs when there is very low levels of dissolved oxygen in the water. This can occur with increased fresh organic matter in a waterway following a rain event and warm temperatures.

Waikato Regional Council is supporting Fish & Game where we are able to do so, but we note that Fish & Game is the lead agency in the response to avian botulism and their ongoing work is greatly appreciated.

Our initial support to the blackwater event included the removal of dead fish from the Maramarua River in an effort to prevent a botulism outbreak, as well as water quality monitoring at several key locations to determine dissolved oxygen levels. 

We pledged financial support of $5000 to help crews working in the wetland pick up dead birds and fish to lessen the environmental effect.

We have also taken the initiative to develop a multi-agency response for blackwater events/botulism events (as we did in response to drought on the Hauraki Plains after the events of 20/21 and 21/22). In partnership with DOC, F&G and mana whenua, we will be looking at:

• clarity on roles and responsibilities across agencies
• what are the longer term science, investigations and monitoring we need to do to recognise these events before they happen
• what are the trigger points for action
• what can we do to reduce frequency and severity of events in the short, medium and long term
• how do we better coordinate action across agencies.

We are continuously looking for ways to improve our freshwater environments.

For example, through Plan Change 1 we are seeking to control intensification of land use and control the sources of nutrients and sediments into the Waikato and Waipa rivers. Unfortunately, this has been a prolonged process that currently sits under appeal to the Environment Court.

Sarah Lealand, Waikato Regional Council Lower Waikato Zone Manager, says:

We are working with landowners in the Waikare and Whangamarino catchments on hill country and streambank stabilisation as part of our Ngā Wai o Waikato project and have also invested significantly in stabilisation works along the reaches of the Pungarehu canal, which connects the Whangamarino wetland and Lake Waikare. Through hill country and bank stabilisation, we are able to reduce the discharge of contaminants, such as sediment, into our waterbodies and wetlands.

The flood scheme provides an important function in protecting rural and residential properties and key national infrastructure, such as roading from flooding.

We are continuously improving our management of flood protection infrastructure to include sustainability, including removing barriers to native fish migration to the sea through our Pathways to the Sea programme.

Proposed plan change 1: more information

Due to the international importance of this wetland and significant values, there are separate rules in the decisions version of plan change 1 that apply to properties draining into the wetland. Read more in the fact sheet here. [PDF, 886 KB]