Fishers never see it. Not because it hides well, though it does. Because it lives in places people avoid. Swamps thick with raupo and sedge. Water black with tannins. Mud deep enough to swallow a boot. The black mudfish exists in these marginal spaces, overlooked and undervalued until it disappears. Kōwaro. The Māori name applies to mudfish generally. Early Māori caught black mudfish by hand in shallow swamp waters or using simple traps. The flesh was sweet and nutritious, valued particularly in winter when other food sources were scarce. Settlers also consumed mudfish but found preparation laborious compared to conventional fish. Today the species serves as an indicator of wetland health in northern regions. The black mudfish reaches about 180 millimetres in length, larger than most other mudfish species. Its body is cylindrical and elongated, coloured dark brown to black with irregular lighter markings. It lacks pelvic fins, giving it a snake-like appearance when moving through dense vegetation. This streamlined shape allows navigation through thick swamp plants and burrowing into mud when water levels drop. Spawning occurs in spring and summer. Eggs are laid amongst submerged vegetation in shallow water. The larvae hatch and remain in freshwater, completing their entire life cycle without marine migration. Diet consists of aquatic insects, terrestrial items, and small crustaceans. The fish feeds on drifting prey caught in current or picked from plant surfaces in shaded swamp sections. Threats come primarily from habitat loss. Wetland drainage for agriculture has destroyed much of the black mudfish's historic range across the northern North Island. Remaining populations persist in protected swamps and undeveloped wetlands. Introduced predators such as trout do not typically inhabit swamp environments, providing some natural protection. However, habitat fragmentation isolates populations and reduces genetic diversity. Climate change may alter rainfall patterns, affecting the frequency and duration of drought periods that mudfish rely on for survival. Classified as Nationally Vulnerable, the black mudfish faces an uncertain future. Its distribution is restricted to specific northern catchments where suitable wetland habitat remains. Each remaining population represents a genetic reservoir potentially vital for species survival. Conservation efforts focus on protecting remaining wetlands from drainage and development. Working with landowners to maintain suitable hydrological regimes offers hope. But the demands of agriculture are immense. The swamps feed the nation when drained. The mudfish requires only intact wetland habitat. Reconciling these needs determines whether the black mudfish persists or joins New Zealand's growing list of threatened freshwater fish.