Information on natural mortality rates of the mackerel icefish (Champsocephalus gunnari) from the period prior to known large-scale commercial harvesting is discussed. After careful consideration of the data and available methods, several errors are noted in earlier estimates. Unfortunately, because none of the datasets are sufficiently comprehensive, it is impossible to unequivocally provide an estimate that is unaffected by confounding effects mainly due to recruitment variation, but also possibly due to age-dependent mortality and commercial fishing.