Ducks Unlimited NZ

Displaying items by tag: Threatened species

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
Friday, 23 February 2018 21:16

Crayfish (Koura) anyone

When I was a kid (and that was a while ago), there was a stream a couple of gullies away from our place with freshwater crays (koura) living there. They were not big but they did taste good.

On a camping holiday at Taupo there was the  opportunity to head off to the lake outlet and dangle tempting tit bits on string and pull up a few koura, and they were slightly bigger than the ones at home.

So it was with interest that recently I read  about a South Island forestry company who decided to stock their fire-fighting ponds with  fresh water crayfish. What a smart idea. They now have 400 ponds.

Takes a while for the little koura to get big enough to provide a good meal, and I don’t know how they would co-habit with ducks, but for those with a good sized pond/lake it just might be a new idea.

It seems their distribution is shrinking through loss of habitat. So this could be an interesting venture or hobby it you have the right sized water area. The Department of Conservation  regard them as a threatened species, so if you lean more toward conservation than a good  meal, this could be an opportunity to do a bit for their survival.

Koura may possibly prefer free flowing water so a quiet pond might not be their home of choice.

But don’t be in a rush to eat them – it takes a while for them to reach eatable size. Feeding them might help. Oh - and you do need a permit if you consider farming them as a commercial venture.

Liz Brook

Published in Issue 166
Saturday, 23 December 2017 22:23

Whio in decline

Whio in decline…

The whio (blue duck) is one of New Zealand’s ancient endemic waterfowl species and is classified as Threatened (Nationally Vulnerable) in the New Zealand Threat Classification System 2012, and listed as Endangered on the IUCN Red List of Threatened Species.

North Island and South Island whio populations are genetically distinct (though they are not described as sub-species) and are treated as separate management units. The whio has experienced rapid declines (particularly in the South Island) in abundance and distribution, nowhere common. It lives at low densities in severely fragmented populations. The most recent estimate of total population numbered 1200 pairs at most. 

The most notable decline driver comes from introduced mammalian predators, with predation of eggs, young and incubating females. Stoats are the most significant threat and stoat control is a main focus of management activities. 

The blue duck’s widespread decline throughout South Island beech forests areas has highlighted the insidious effects of mast-seeding beech trees, which result in great predation pressure, as rodent populations explode, causing a lagged increase in stoat populations which seek alternative prey when rodent numbers crash. A malebiased sex-ratio throughout the range, indicates that predation during incubation is significant. 

One of the major conservation management tools for whio is captive breeding for release into the wild. The blue duck has been held in captivity for many years, and its husbandry requirements are understood. The aim is to maximise productivity of the captive breeding programme, and ensure that captive-bred ducklings are released at the highest priority sites. Captive breeding has proven highly effective, and is vital in aiding the recovery programme with the re-establishment and rebuilding of viable populations throughout the former range.

The Isaac Conservation and Wildlife Trust provides the largest output of blue duck juveniles annually, with its waterfowl aviaries being the most successful captive breeding enclosures in New Zealand for North Island blue duck. The Trust currently holds two North Island blue duck breeding pairs. These breeding pairs can lay up to three clutches per season, with an average of six eggs per clutch. All eggs are collected for incubation and hand rearing.

The Trust is a significant participant in the WHIONE programme, which consists of retrieving wild eggs each breeding season from South Island pairs for artificial incubation and rearing in captivity, with a subsequent release of juveniles once fledglings have been hardened in our fast water facilities and are at a lower risk of predation. Releases take place in natal territories or at new sites around the South Island to increase numbers and genetic diversity across sites  or re-establish lost populations.  Since 2016 the Trust has been retaining cohorts of South Island blue duck juveniles for flock mating, to initiate a captive breeding population across several South Island facilities. The Trust will move out of North Island birds and hold three pairs of the South Island blue duck.

Each season for the last 12 years, the Trust has also received North Island blue duck juveniles bred by other captive institutions nationwide, which are transferred for pre-conditioning in fast flowing raceways prior to release into the wild.

Sabrina Luecht

Wildlife Project Administrator

The Isaac Conservation and Wildlife Trust

Published in Issue 171