A native freshwater fish, thought to be lost from a west Auckland wetland, has been rediscovered after a decade long search, with a healthy population of both adults and juveniles found.
The elusive waikaka, or black mudfish, are reproducing themselves in a Helensville wetland, despite the area being chock-full of vegetation which limits habitable areas.
Nine fish were found, including juveniles, hiding in isolated, shaded, water-filled depressions.
“They’re quite muted, not flashy or colourful but they’re kind of cute,” said Auckland Council’s senior regional adviser (freshwater) Matt Bloxham.
“This tiny fish may be secretive, but its survival depends on us noticing it, protecting and carefully managing its wetland habitats.”
The rediscovery of the fish after a decade of searching the Helensville wetland was significant. Black mudfish have a ‘Threatened – Regionally Critical’ conservation status in Auckland, with just six known populations in the entire region.
“[It] shows these fish are making a go of things and reproducing in these tiny pockets of wetland.”
The black mudfish (Neochanna diversus) is one of New Zealand’s most unusual and resilient freshwater fish species. The small, eel-like creatures complete their entire life cycle within wetlands - they never head to sea like most native fish species.
Bloxham said it makes them particularly vulnerable, and if their wetland habitat was lost or degraded, an entire population could disappear with it.
Auckland has already lost over 97% of its original freshwater wetland area.
Council’s general manager environmental services Samantha Hill said every rediscovery was a vital win for biodiversity.
“Each new population found, helps secure the species’ future in the region and guides how we manage and protect these special wetland habitats,” Hill said.
“What we hope to do in these instances is work closely with landowners to control invasive weeds and predators, restore wetland buffers, and where necessary, restore a wetland’s hydrology.”
Black mudfish thrive in shallow, secluded pools shaded by native wetland vegetation, which provides both cover and a buffet of falling insects to feed on.
Mudfish are also famous for their survival skills, able to endure months without water by burrowing into damp mud or hiding beneath logs and slowing their metabolism until the rain returns.
Bloxham said this gave them an advantage over would-be competitors.
“Juvenile eels that manage to reach these secluded, temporary pools are forced to leave before they grow large enough to predate resident mudfish.”
The rediscovery adds to a decade-long programme to protect black mudfish, which began in 2014.
Since then, council staff have found new populations, rediscovered old ones, and worked with Auckland Zoo to explore captive breeding and rewilding opportunities.
“Mudfish are cryptic, but they’re also unpredictable and seldom found reliably in the same locations, which unfortunately makes it hard to find and monitor.”
LDR is local body journalism co-funded by RNZ and NZ On Air.
