New Zealand is home to five species of mudfish - and despite the unassuming name, these cigar-shaped little fish have some pretty amazing survival tactics!
Mudfish are freshwater fish that love to live in wetlands or other soggy areas. What's special about these torpedo-like wee fish is that they can exist without water for months at a time by burying themselves in damp soil, leaf matter, or under tree-roots until it gets wetter again. Early European explorers used to come across mudfish in the soil while they were digging for root vegetables - our first "fish and chips", according to some keen DOC freshwater rangers.
Mudfish truly are a "fish out of water", by being able to exist without water for months on end, slowing down their metabolic rate and breathing oxygen through their skin (which, incidentally, isn't scaly but smooth). Canterbury mudfish will come to the surface and take a big bubble of air in oxygen-depleted water.
During drier periods, mudfish simply dig deep (well we think they do, nobody's recorded them doing it yet), wriggle into the soil and hang tough waiting for wetter times to come. They are able to dig deep, due to strengthened bones in their head and a flattened shape to their skull, making them perfectly adapted to shovel down into moist soil to rest until things get wetter.
This kind of fishy hibernation is called aestivation, and unlike hibernating animals who wake up fairly groggy, all it takes to kick these fish back into gear is being immersed in water again - at which point they wriggle away as if they hadn't just spent the previous two months in suspended animation. (I would love to know their secret, since I can barely get going on a Monday morning.)
Mudfish aren't terribly territorial, which means they can exist in high numbers with the right conditions. The problem for the younger generation is that the adult mudfish (which can grow to about the size of a good cigar) are not terribly fussy about what or who they eat. A younger, smaller mudfish makes a tasty meal to an adult. The mudfish get around this by swapping their lifestyles around: the young ones come out during the day, and hide at night when the nocturnal adults are feeding.
Despite their fascinating survival strategy, our mudfish are in trouble. Though their name suggests otherwise, mudfish appear to prefer clear water and, sadly, drainage of some of their prime habitats (many mudfish remain on private land) has sucked the life out of the places they could live. Drainage and vegetation clearance has occurred on such a large scale around the country that habitats are much drier and the mudfish are pushed to their absolute limit in terms of being able to exist out of water.
The good news about mudfish is that they aren't quite as "high maintenance" as some of our other freshwater fish, and as long as they have fairly high quality water and the right aquatic plants around, mudfish can live in high numbers in wetlands, ponds, drainage ditches, culverts, water races and irrigation areas. The point is, if you have mudfish on your land, you can continue to farm responsibly while being lucky enough to hang on to your mudfish. If you're not sure, talk to your local DOC office.
I think part of the mudfishes' PR problem (apart from the name!) is that the adults are nocturnal, so are not often seen, and perhaps people don't seem to get how awesome they are! (Though hats off to the Canterbury mudfish supporters who created this website, and hosted a Mudfish Day in celebration of their discovery). The other issue mudfish face is that there is not a lot of formal protection for them, since A) we don't know where they all are, and B) it's likely that many exist on private land. Anyway, I reckon it's time for an image makeover for mudfish, a "rebranding", if you will. They're staunch, hardworking (well think of that digging they must do!), and tenacious wee fish. I'm keen to know if you've ever seen them, or if you know of any in your patch? Did you know about their superfish powers?
They're not kakapo or kiwi and we all know that cute is king, but why not make a fuss for mudfish?
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