The Ross Sea has been geologically characterized by tectonic and glacial processes. These processes have created diverse habitat, including distinct banks and basins. For many fish species the availability of habitat is critical to the long-term viability of the population. Antarctic toothfish (Dissostichus mawsoni) are subject to an increasingly important commercial fishery in the Ross Sea and yet little is known about habitat associations for different life history stages. To define and assess the availability of habitat for Antarctic toothfish a benthic habitat map of the Ross Sea was created based on the habitat mapping scheme developed by Greene et al. (1999). Fish age data from the long-line fishery in the Ross Sea were superimposed on the habitat map and broken into discrete spatial areas. Differences in age distributions between these areas were found using ANOVA. These distributions were consistent with an ontogenetic movement of fish from shallow continental shelf habitats to deep-water continental slope was documented. Younger, less mature fish were located on the continental shelf and older fish were located on the continental slope. In addition, the older and most mature individuals were found on ridges in the northern Ross Sea, consistent with the hypothesis of an austral summer spawning migration from continental slope to the ridge habitat of the North Ross Sea. An effective management strategy might focus on protecting the northern ridge habitat to maintain long-term viability of Antarctic toothfish populations.