Respiration of antarctic fish from McMurdo Sound.

1. Resting rates of oxygen uptake were measured for nine species of unstressed fish living at -1.8 degree C in McMurdo Sound, Antarctica (77-78 degrees S). Interspecific differences in VO2 were correlated with the habits and activity of the fish. 2. The cryopelagic Pagothenia borchgrevinki regulated oxygen uptake down to a critical PO2 of approximately 60 mmHg. The inactive benthic species Trematomus centronotus extracted oxygen to lower PO2 and appeared to have a lesser degree of oxyregulation when the data were analysed using a quadratic model. 3. Cutaneous oxygen uptake in the nototheniids T. bernacchii and P. borchgrevinki amounted to 9 and 17% of total VO2 under normoxic conditions which is less than that reported for scaleless Antarctic fish. 4. The contentious concept of metabolic cold adaptation in polar fish has been reviewed, and the opinion expressed that the phenomenon cannot be dismissed on the grounds of technically incompetent measurement, or through inappropriate extrapolation of data from fish at lower latitudes.