Population dynamics and life-history plasticity of mackerel icefish (Champsocephalus gunnari) within the vicinity of Heard Island and the McDonald Islands

Mackerel icefish (Champsocephalus gunnari) are found associated with sub-Antarctic islands and continental shelves in the Atlantic and Indian sectors of the Southern Ocean between the Polar Front and the Southern Boundary of the Antarctic Circumpolar Current. Mackerel icefish are one of the most common fishes encountered across the shallow (<500 m) Kerguelen Plateau north of 60°S. The species was targeted in this area by unregulated fisheries in the 1970s until fishing ceased due to low catch rates, the declaration of the French exclusive economic zone (EEZ) around Iles Kerguelen and the Australian Fishing Zone around Heard and McDonald Islands (HIMI). Commercial fishing of mackerel icefish by Australian vessels at HIMI commenced in 1997 and continues to this day. Catches are characterised by high interannual variability, due in large part to the population being dominated by a single year class, resulting from recruitment that occurs on a three-year cycle.