Impact of environmental variability on mackerel icefish (Champsocephalus gunnari) on the Kerguelen Plateau

Background

Climate change is already impacting marine ecosystems around the world, and this trend is likely to increase in the future. The effects of climate change are exacerbated by extreme events such as marine heatwaves, which have become increasingly common in recent years. The Southern Ocean is projected to exhibit significant environmental changes due to anthropogenic climate change over the course of this century and such physical changes are expected to flow through to impact upon the marine ecosystems in the region.

One area of the Southern Ocean that has experienced significant heatwaves in recent years is the Kerguelen Plateau. The Plateau is located in the Indian sector of the Southern Ocean and rises steeply from abyssal depths forming an oceanographically complex region. It also harbours a diverse and productive ecosystem. Mackerel icefish are a key component of this ecosystem; they mostly found in relatively shallow waters (<250 m), are an important link in the food chain and are the target of a small commercial fishery.

Aims/Objectives

This project will draw upon and extend recently completed work that characterises marine heat waves on the Kerguelen Plateau. It will explore the relationship between environmental variability and variability in the abundance of Mackerel icefish (Champsocephalus gunnari) and the related unicorn icefish (Channichthys rhinoceratus) in the region. It seeks to understand how heatwaves and other environmental factors have affected icefish in recent decades and what the likely impacts of future environmental conditions will be.

Methods

The estimates for icefish abundance and population structure will be derived from annual stock assessments which are based on a Random Stratified Trawl Survey (RSTS) and have been conducted by the Australian Antarctic Division since 1997. The RSTS records counts of icefish as well as biological parameters such as length, weight and condition. Spatio-temporal models will be used to understand how past variability in abundances and other biological parameters relates to environmental variability. The statistical relationships developed by this approach will then be used to inform the development of quantitative or qualitative models that links icefish population with changing environmental conditions and other components of the ecosystem. Depending on the student’s interests there is also scope to delve more deeply into the biology and ecology of icefish in the region.