Ensemble analysis of the future distribution of large pelagic fishes off Australia

Changes in the climate due to anthropogenic effects are impacting the global oceans and the constituent biology, particularly through changes in water temperature. Impacts of warming water on oceanic species are most likely to be detected as changes in distribution. Pelagic fishes, in particular, respond to changes in ocean temperature, and modify their distribution on seasonal and interannual timescales, and thus are likely to do so in the future. Global climate models provide insight into possible future conditions, but there is also considerable uncertainty regarding future changes because of differences in model structure and future scenarios. To address some of this uncertainty, I considered output from multiple climate models through an ensemble analysis and examined potential changes in the distribution of large pelagic fishes captured by longline fisheries on the east and west coast of Australia by the year 2100. For the east coast, over 95% of model predictions for 14 pelagic species (tunas and billfishes) suggested that core range would move south, and be smaller than what occurs presently. There was less certainty for the west coast, although the core range for all 14 species moved south and was smaller for 63% and larger for 37% of scenario-model combinations. The overall rate of predicted habitat movement for the suite of pelagic species averaged about 40 km/decade. While relatively coarse, these predictions give some confidence to stakeholders about likely changes in future distribution for these regionally important pelagic fishes.