Future Distribution of Suitable Habitat for Pelagic Sharks in Australia Under Climate Change Models

Charlotte A. Birkmanis,Julian C. Partridge,Leigh W. Simmons,Ana M. M. Sequeira,Jennifer J. Freer

doi:10.3389/fmars.2020.00570

Charlotte A. Birkmanis, Julian C. Partridge + Show 3 more

Open Access

https://doi.org/10.3389/fmars.2020.00570

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Abstract

Global oceans are absorbing over 90% of the heat trapped in our atmosphere due to accumulated anthropogenic greenhouse gases, resulting in increasing ocean temperatures. Such changes may influence marine ectotherms, such as sharks, as their body temperature concurrently increases towards their upper thermal limits. Sharks are high trophic level predators that play a key role in the regulation of ecosystem structure and health. Because many sharks are already threatened, it is especially important to understand the impact of climate change on these species. We used shark occurrence records collected by commercial fisheries within the Australian continental Exclusive Economic Zone (EEZ) to predict changes in future (2050 to 2099) relative to current (1956 to 2005) habitat suitability for pelagic sharks based on an ensemble of climate models and emission scenarios. Our predictive models indicate that future sea temperatures are likely to shift the location of suitable shark habitat within the Australian EEZ. On average, suitable habitat is predicted to decrease within the EEZ for requiem and increase for mackerel sharks, however, the direction and severity of change was highly influenced by the choice of climate model. Our results indicate the need to consider climate change scenarios as part of future shark management and suggest that more broad-scale studies are needed for these pelagic species.

Highlights

Climate change is predicted to have unprecedented effects on the marine environment, with changes in ocean temperature increasing extinction risk for many species (Dulvy et al, 2003; Barnosky et al, 2011; Bruno et al, 2018; Pinsky et al, 2019) and altering the global distribution of marine life (Tittensor et al, 2010; Garciá Molinos et al, 2016)
Our results show that the predicted mean sea-surface temperature (SST) anomaly ranged from minima of 0.93◦C and 0.69◦C, to mean maxima of 1.83◦C at the end of the century (Figure 1 and Table 1)
The resulting predicted habitat suitability maps are presented as the mean across all climate models for requiem (Figure 2) and mackerel sharks (Figure 3), with the predicted change per climate model presented in Figures 4, 5

Summary

Introduction

Climate change is predicted to have unprecedented effects on the marine environment, with changes in ocean temperature increasing extinction risk for many species (Dulvy et al, 2003; Barnosky et al, 2011; Bruno et al, 2018; Pinsky et al, 2019) and altering the global distribution of marine life (Tittensor et al, 2010; Garciá Molinos et al, 2016). Sharks may be influenced by climate change (Bernal et al, 2012; Rosa et al, 2014, 2017; Syndeman et al, 2015; Pinsky et al, 2019), with higher temperatures increasing their metabolism and oxygen demand (Pistevos et al, 2015; Lawson et al, 2019). The exception to this may be Lamnid mackerel sharks, which have some endothermic capability (Watanabe et al, 2015)

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