Preliminary results of a pop-up satellite tag (PSAT) on large Antarctic toothfish are described in this report. The toothfish was caught in the Mawson Sea in Feb 2015 and released with a PSAT by a Korean scientific observer. The same observer recovered the fish a year later. The days of liberty were over a year (366 days). The vertical movement of the fish shows strong and contrasting patterns. The most significant pattern was the fish staying at the same depth for a couple months. The vigorous diel vertical movement period followed after. It occurred during winter to early spring that it may be indicating the possibility of a spawning behavior.