The waikaka or black mudfish (Neochanna diversus) is a fish of the family Galaxiidae,[1] found only in swamps and wetlands in the northern half of the North Island of New Zealand, from Kaitaia in the north to the Mōkau River in the south.

[3] N. diversus differs from brown mudfish, N. apoda, in its "conical teeth in the jaws, the lower number of rays and the higher proportion of branched rays in the dorsal and anal fins, the shorter mouth and greater convexity of the profile of the snout.

N. diversus is listed as At Risk - Declining under the most recent assessment (2018) of the New Zealand Threatened Classification for fishes.

[6] Efforts by the New Zealand Department of Conservation and regional councils have helped protect and reintroduce the fish.

[4][8] The species is found in wetlands and streams that have still or gently flowing waters.