Tiny but mighty: black mudfish rediscovered in Helensville wetland
A little-known native freshwater fish thought lost from a local wetland has resurfaced. The elusive Waikaka, or black mudfish, has been rediscovered in a Helensville wetland, with both adults and juveniles found, proving these shy creatures are reproducing themselves.
Auckland Council’s Senior Regional Advisor (Freshwater) Matt Bloxham says they were cautiously optimistic about the find as the wetland had become choked with invasive vegetation, reducing the size pools and wet habitable areas.
“But discovering nine fish, including juveniles, hiding in isolated, shaded, water-filled depressions show 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. These small, eel-like creatures complete their entire life cycle within wetlands; they never head to sea like most native fish species.
That makes them particularly vulnerable; if their wetland habitat is lost or degraded, an entire population can disappear with it. Auckland has already lost over 97 per cent of its original freshwater wetland area.
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.
“This gives 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,” adds Matt.
The rediscovery is particularly significant because black mudfish have a ‘Threatened – Regionally Critical conservation status in Auckland. There are just six known populations in the entire region.
The recent find was made during a joint Auckland Council/Watercare survey, targeting wetlands with the right mix of native vegetation to support mudfish.
Auckland Council’s General Manager Environmental Services Samantha Hill says every rediscovery is a vital win for biodiversity.
“These rediscoveries give us hope and a clear pathway for restoration and management.
“Each new population found, helps secure the species’ future in the region and guides how we manage and protect these special wetland habitats.
The rediscovery is particularly significant because black mudfish have a ‘Threatened – Regionally Critical conservation status in Auckland. There are just six known populations in the entire region.
The recent find was made during a joint Auckland Council/Watercare survey, targeting wetlands with the right mix of native vegetation to support mudfish.
Auckland Council’s General Manager Environmental Services Samantha Hill says every rediscovery is a vital win for biodiversity.
“These rediscoveries give us hope and a clear pathway for restoration and management.
“Each new population found, helps secure the species’ future in the region and guides how we manage and protect these special wetland habitats.
‘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,” says Hill.
Shade is also crucial for preventing the pools from drying out and keeping fish cool during Auckland’s warmer months.
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. The goal is to establish self-sustaining wild mudfish populations that can withstand regional threats like land-use change and drought.
“They’re quite muted, not flashy or colourful but they’re kind of cute,” Bloxham admits with a grin.
“This tiny fish may be secretive, but its survival depends on us noticing it, protecting and carefully managing its wetland habitats. 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. Securing a network of small, shaded and secluded wetland pools for mudfish is part of the solution” says Matt.
The discovery has also sparked fresh hope and led to searches in nearby wetlands which netted a second population within a month of the first, signaling there may still be wetlands supporting small mudfish populations out there. The search goes on.
While the black mudfish may be small, its story is mighty and a reminder that even the quietest corners of our wetlands can hold extraordinary surprises.
