Shedding new light on the life cycle of mackerel icefish in the Southern Ocean

Mackerel icefish (Champsocephalus gunnari) has a widespread distribution in the Atlantic and Indian Ocean sectors of the low-Antarctic region. Biological characteristics differ considerably between populations in the southern Scotia Arc and those living further to the north. Fish living in the north mature one year earlier than in the south. They have a much shorter life span and die after they have spawned for 2 – 3 times. The number of eggs produced per gram of body weight is higher in the north. Stocks have declined in most parts of the distributional range due to the impact of fishing and due to natural causes. Increases in populations of Antarctic fur seals at South Georgia and parts of the Indian Ocean appear to have led to increased predation on stocks of icefish. Shifts in hydrological regimes in the northern part of the distributional range have either started to lead or will lead to deteriorating living conditons for C. gunnari in the near future. Fish stock assessment under CCAMLR needs to take these constraints into consideration when providing advice on total allowable catches for fisheries management.