Where are Canterbury mudfish found?
This map shows records of Canterbury mudfish habitat from NIWA’s New Zealand Freshwater Fish Database – you can find more information here.
There are distinct clusters in the records for Canterbury mudfish habitat. These hotspots relate to where large inland and coastal wetlands were before European land development.
If you live in one of these areas, you could possibly have mudfish on your property.
The populations are now highly fragmented and mudfish can occur in small pockets of habitat. It’s likely that not all of these have been found.
What does mudfish habitat look like?
There is little, if any, unmodified habitat left and it is difficult to say what mudfish would have preferred. Maybe it was pools within boggy kahikatea forests, or thick flax swamps, or maybe amongst the sedges and rushes around groundwater springs.
Today, Canterbury mudfish are found in a wide range of places, from small springs, wetlands and willow bogs to more modified habitats such as water races, roadside drains and farm ponds; basically, any suitable aquatic habitat that is left.
What most habitats have in common is that water flow is slow or absent. Aquatic plants also grow well in these habitats and there may be more silt than cobbles present.
However, there are many habitats that look suitable but mudfish are not present because they dry out too much or there are too many eels or other fish species.
How do I find out if mudfish are present?
Adult mudfish are only active at night so are rarely seen. However, their young actively forage out in the open in the water for about a month until they are around 30 – 40 mm long. These young fry can be seen during spring and early summer and look like small, dark-coloured, wiggly whitebait.
To spot them, you need to spend several minutes looking carefully through the water at several locations. Still, sunny afternoons are the best time to look as the water surface is calm and sunlight helps, as it is often easier to spot the moving shadow of the small, semi-transparent fish.
There are other common native species that have similar looking fry so if you spot something, contact DOC or a fish expert and they can check which species is present by catching some adults.
Once you know you have mudfish, you can look for fry each year to check they are still present and reproducing. This would be important to do after droughts or if you were making changes that might affect their habitat.
What should I do if I have mudfish on my property?
The persistence of mudfish indicates that responsible land and water management has been practised.
So if it isn’t, broken don’t fix it.
Maintain the status quo as much as possible, especially if mudfish are thriving.
But, if changes to land or water-use are planned, then options for protecting habitat may need to be considered.
General guidelines for managing waterways on farms may apply.
Except that sometimes the opposite guidelines may apply!
Mudfish habitats don’t need to be heavily shaded with trees and shrubs as recommended for other species or larger streams. Also avoid planting deciduous trees as their leaves may overload small habitats and ponds.
Downstream barriers to fish, such as overhanging or badly installed culverts, may protect mudfish habitat by preventing other fish (that might prey on mudfish) from invading upstream.
How do I clear a race or drain of aquatic plants if mudfish are present?
Aquatic plants, even those considered weeds, are important for mudfish as cover from predators and to lay their eggs on.
- Clear out aquatic plants in autumn.
- Avoid removing aquatic plants during late winter and early spring when they might be covered with tiny, transparent mudfish eggs.
- This can remove an entire generation!
Try to leave areas that are not problematic; every small patch of plant cover matters.
Find a balance
Not too much and not too little.
Ideally, water should flow freely and there should be plenty of plants growing in the water along the bank edge.
There is much technical information about the biology and ecology on the Department of Conservation’s website.
You may also wish to read the Department of Conservation's plan for mudfish recovery for the years 2003 - 2013. (Right side of page at top)
One of the key scientists researching mudfish habitats in Canterbury is Dr Leanne O’Brien.
Below, her reports are available for download:
“50 facts about Canterbury Mudfish” ( 608 kB) compiled by Dr Leanne O’Brien
The conservation ecology of Canterbury mudfish ( 2.04 MB) ~ Neochanna burrowsius, DOCTORAL THESIS SUMMARY, School of Biological Sciences. University of Canterbury, Dr Leanne K. O’Brien, 2006.
For more information, visit the Ichthyo-niche website at: www.i-niche.co.nz.
More Mudfish Information
Mysterious Mudfish: See a mudfish video! Department of Conservation website.
Mudfish Facts: from the Department of Conservation website.
Up the Creek: a bilingual website for students which follows Dion, Rick, and Ani on a trip up the creek as they learn how freshwater supports life.
Drawing by Bob McDowall