Inter-annual variation in the gonad cycle of the mackerel icefish

Spawning by Antarctic fish is generally considered to be seasonal and restricted to a brief period during the autumn and winter. Arising from this it has been assumed that the gonadal maturation cycle is also closely associated with the time of year. The gonad maturation cycle of the mackerel icefish Champsocephalus gunnari was investigated using data collected during research surveys and from sampling the commercial fishery. Spawning appears to occur at the same time each year, but the timing of gonadal development is subject to a considerable inter-annual variation. The implications of this variation are discussed with respect to feeding conditions.