Ducks Unlimited NZ

Displaying items by tag: Mudfish

Saturday, 09 November 2019 22:31

Fish deaths call for relocation project rethink

When more than 900 brown mudfish in the Wairarapa were transferred to a new wetlands habitat to make way for wastewater storage reservoirs, the district council initially claimed it was a success, but it was later learnt that most of the fish did not survive.

Fish & Game reported that the project in December and January involving 921 mudfish, organised by Carterton District Council, had resulted in virtually none surviving.

In July Greater Wellington Regional Council told the Wairarapa Times-Age that it would undertake further monitoring of the translocated population and would be tracking how the mudfish and their habitat were doing.

“Our immediate focus is on creating additional habitat that we believe will be more suitable for brown mudfish,” it said. “Once we are happy that this new habitat is established, we will relocate the remaining mudfish.”


GWRC believed mudfish were still present in the wetland where they were relocated, but in lower numbers.

“Unfortunately, the habitat created did not develop as we had hoped, in particular in relation to the aquatic vegetation cover that would have provided cover for the mudfish.

“High water temperatures and predation by birds, such as shags and herons, are considered to be among some of the key issues that impacted on the success of the translocation.”

GWRC will continue to work closely with the district council to create a new habitat more similar to the original area the fish were relocated from.

“We will be incorporating the learnings so far to ensure that the project has the best chance of success, in terms of maintaining and enhancing brown mudfish habitat.”

The project will now be led by Alton Perrie, an environmental scientist from GWRC who has “considerable expertise in mudfish”.

Fish & Game Wellington manager Phil Teal has called for an independent inquiry by the Department of Conservation into the transfer.

A Fish & Game senior scientist even advised the project co-ordinators last year that this project was not advisable.

“This is $160,000 of ratepayers’ money that would be much better used on meaningful conservation projects that would benefit all fish habitat,” he said.



Published in Issue 177
Saturday, 09 November 2019 22:26

Versatile mudfish underrated

Most New Zealanders are unaware of the existence of this little known but special species of fish, let alone seen one. If you were to cross an eel with a whitebait – this is what the Canterbury mudfish looks like.

Small, tubular and lacking scales, the adults are 10 to 12cm long, generally nocturnal and are restricted to small isolated freshwater locations, so are seldom seen. The juveniles feed during the day, hiding at night to avoid being eaten by their adult counterparts.

Mudfish may appear unspectacular, but they have some very special characteristics and they are part of our treasured taonga.

To allow them to survive in periods of drought, mudfish bury themselves in damp surroundings such as under logs, tree roots or vegetation to wait for surface water to return. By slowing down their metabolic rate and breathing oxygen through their skin, mudfish can survive up to two months out of water!


There are five species of mudfish and all are classified as either threatened or at risk under the New Zealand Threat Classification with the most threatened being the Canterbury mudfish.

At the Isaac Conservation and Wildlife Trust in Christchurch, a focus to increase numbers of Canterbury mudfish is being achieved by optimising their pond environment to promote their establishment, removing predator fish species such as eels, trout and salmon and working closely with DOC to monitor and study this endangered species.

A threat to all species of mudfish across New Zealand is the depletion of habitat by the draining of swamps, wetlands and the modification of waterways and drains through mechanical clearance.

Simple mudfish habitat protection can be achieved through:

  • Fencing off the wetland from stock to prevent wetland plants being grazed and trampled.
  • Plant a native vegetation buffer and DOC can recommend suitable plants for riparian planting.
  • Prevent invasive fish species establishing by finding out which species are in your catchment and taking care not to accidentally introduce them.
  • Maintain drains and waterways using mudfish friendly methods. Create shade on the margins to minimise growth of freshwater weeds. If physical weed removal is required, clear short sections at a time.

The benefits of wetland protection and expansion are advantageous also for native bird and invertebrate species, allowing them to flourish and multiply for future generations.


Catherine Ott is the administration manager for the Isaac Conservation Land Wildlife Trust.



Published in Issue 177