Impacts of environmental variability on the Kerguelen Plateau marine ecosystem

Stuart Corney, University of Tasmania, Hobart, TAS, Australia, Nicole A Hill, Institute of Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia, Gabriela Semolini Pilo, Institute for Marine and Antarctic Studies, Hobart, TAS, Australia and Neil John Holbrook, University of Tasmania, Institute for Marine and Antarctic Studies, Hobart, TAS, Australia
The Kerguelen Plateau is home to a significant Patagonian toothfish fishery, worth over USD50 million a year in the Australian sector alone, as well as being home to significant populations of seals, seabirds and whales. These populations are supported by the increased primary production that is consistently observed in the eddy-field caused by the interruption of the ACC as it moves around the plateau.

In 2016, the Australian longline fishery on the Kerguelen Plateau experienced lower than average catch rates for most of the season between April and November, especially in the early part of the season where the rate was about 50% of the 2011-2015 mean. Longline catch rates were again low at the start of the 2017 fishing seasons, but then rapidly recovered to a large degree by June. A preliminary investigation concluded that the declining catch rates were unlikely to be caused by a decline in fish stock biomass, but instead could have been related to a change in fish catchability driven by fish behaviour and environmental factors.

This presentation will discuss the results of our investigation into the frequency, intensity and depth of marine heatwaves on and around the plateau. The investigation indicates that the full-depth temperature on the plateau has been increasing over the past 20 years and that this has made heatwaves more likely. The drivers and mechanisms for surface and sub-surface heatwaves in the region will be presented. Finally results of investigations into the impact that changes in environmental conditions, such as marine heat waves, have on the Patagonian toothfish and the marine ecosystem of the plateau will be presented.