Department of Conservation | Te Papa Atawhai
https://www.doc.govt.nz/
https://www.doc.govt.nz/
Introduction
The black mudfish can be found in Waikato, Auckland and Northland. It is unique to New Zealand and found nowhere else in the world.The black mudfish can be found in Waikato, along with Auckland and Northland. It is unique to New Zealand and found nowhere else in the world.
Once widespread, they have disappeared from many areas in the lower Waikato, Hauraki Plains, Auckland and Northland mostly due to continuing loss of habitat (up to 90% of Waikato wetlands have been lost), invading pest fish and plants (ie willows) reduced water quality (especially sediment). Increasingly dry climate, ongoing drainage and water abstraction also mean our wetlands are getting dryer and more likely to burn.
Black mudfish have a conservation status of At Risk–Declining under the NZ Threat Classification System.
Black mudfish
Life on the edge
Like other mudfish species, black mudfish have a number of very unusual adaptations for the wetlands and peat ponds in which they live. Mudfish are specially suited to living on the edges of wetlands where summer drying excludes competing and predatory fish species like eels, allowing mudfish to thrive.
When their wetland habitats dry out over summer, they can survive out of water, sometimes for several months, by burrowing into moist areas under tree roots or into peat, mud or damp leaf litter.
During this time, black mudfish slowly lower their metabolism, reducing the amount of energy they need to live (in a similar way to hibernating bears, and sometimes known as 'aestivation' in mudfish), but immediately wriggle into life when water returns.
Their skin is coated in tear-like mucus, which helps keep them moist out of water and also protects the fish against infection, and they absorb oxygen through their skin.
Black mudfish populations can be found at Whangamarino Wetland in Waikato
Threats
Despite these clever adaptations, black mudfish have very specific habitat requirements, and are particularly vulnerable to habitat loss, pest fish and water quality decline.
How you can help
The main way to help mudfish is by preserving and improving their habitat for example by:
- Fencing stock out of wetlands and upstream waterways.
- Plant harakeke/flax and native sedges like carex and toetoe (not pampas) along stream banks and drains. Vegetation rooted in shallow water in and around farm drains helps provide black mudfish with shelter and food and reduces the water temperature, retaining moisture which is essential for mudfish survival.
- Clear farms drains less frequently, retaining vegetation to provide habitat and shade. Use a digger-arm to protect drain-side vegetation.
- Ask your digger drivers to follow a check-clean-dry approach to keep your waterways from pest fish and plants.
- Protect wetlands on your property. As well as being mudfish habitat, wetlands filter farm run-off and help keep the streams clean.
- Establishing new populations by translocations has proven difficult as the specific habitat that black mudfish prefer are hard to create from scratch. But if the right habitat exists or can be enhanced then new populations can be established.
- Create a farm management plan that includes nutrient budgeting, effluent disposal and sustainable peatland management. You can get help with creating farm management plans with the help from your Regional Council, DairyNZ or NZ Landcare Trust.