The closely related New Zealand native galaxiid species inanga (Galaxias maculatus), banded kokopu (Galaxias fasciatus) and black mudfish (Neochanna diversus) inhabit distinct oxygen environments and have been shown to exhibit species-specific hypoxia sensitivities. To investigate whether these differences were based on distinct metabolic oxygen demands, oxygen consumption profiles as a measure of routine metabolic rates at normoxia, mild and severe hypoxia were determined utilising intermittent-flow respirometry. Inanga demonstrated the highest average oxygen consumption at normoxia and mild hypoxia (14.7 ± 0.6 μmol O₂ h^-1 g^-1) and black mudfish the lowest (7.6 ± 0.8 μmol O₂ h^-1 g^-1). All three species were indicated as oxyregulators. Inanga displayed the highest hypoxia sensitivity with a critical oxygen concentration (C_crit) of 5.0 mg L^-1, while banded kokopu were slightly more tolerant (4.3 mg L^-1). No C_crit was ascertained for black mudfish and it was deduced that they had a distinct tolerance towards hypoxia. The hypoxia sensitivities of the three species indicate species-specific metabolic oxygen demands and physiological response capacities. Therefore, habitat preferences of these species are likely a result of adaptive radiation processes in the context of the oxygen environment.