No being does isolation like mudfish
WHEN holed up in solitary seclusion in my house for weeks during the lockdown, my thoughts turned to the Canterbury mudfish, a native galaxiid. The mudfish voluntarily opts for this kind of existence by inhabiting sluggish streams, swamps and small backwaters that periodically dry up. When this happens, it languishes in a small, smoothlined dry hole in the bank. The mudfish can live out of the water like this because it can breathe through its skin alone, both absorbing oxygen and excreting carbon dioxide. When its water channel dries up, it goes into aestivation, which is a state of dormancy or inactivity induced by the heat of summer. While in water, it breathes through its gills in the usual way.
There are five species of mudfish in New Zealand, separated geographically, but all classified as threatened or at risk. The Canterbury mudfish
Neochanna burrowsius (family Galaxiidae), kowaro in Maori, occurs on the Canterbury plains, east of the Southern Alps, from a little north of the Waimakariri River to the Waitaki River. It is long and tubular with a small blunt head, and 120mm150mm long when mature. It lacks scales, and has very small eyes and tiny pelvic fins.
The Canterbury mudfish can be found near the coast in brooks that originate in the Hunters Hills, in streams too small to break through to the sea. These streams are blocked at their mouths by boulders and stones piled up by the waves and enter the sea underground. Streams and rivers sufficiently strong to break through to the sea at the surface in this area lack native galaxiid fish, seemingly because trout can enter such streams and outcompete and also eat the native galaxiids. Tiny drains, ditches, and streams between Mahikihi and Willowbridge contain mudfish, which I have seen in their dry aestivation holes.
The Canterbury mudfish is declining in distribution due to swamp drainage and the demands of agriculture, and is now considered to be a rare and threatened species.