Forecasting intraspecific changes in distribution of a wide-ranging marine predator under climate change

Yuri Niella,Adam Barnett,Robert Harcourt,Paul Butcher,Bonnie Holmes

doi:10.1007/s00442-021-05075-7

Abstract

Globally, marine animal distributions are shifting in response to a changing climate. These shifts are usually considered at the species level, but individuals are likely to differ in how they respond to the changing conditions. Here, we investigate how movement behaviour and, therefore, redistribution, would differ by sex and maturation class in a wide-ranging marine predator. We tracked 115 tiger sharks (Galeocerdo cuvier) from 2002 to 2020 and forecast class-specific distributions through to 2030, including environmental factors and predicted occurrence of potential prey. Generalised Linear and Additive Models revealed that water temperature change, particularly at higher latitudes, was the factor most associated with shark movements. Females dispersed southwards during periods of warming temperatures, and while juvenile females preferred a narrow thermal range between 22 and 23 °C, adult female and juvenile male presence was correlated with either lower (< 22 °C) or higher (> 23 °C) temperatures. During La Niña, sharks moved towards higher latitudes and used shallower isobaths. Inclusion of predicted distribution of their putative prey significantly improved projections of suitable habitats for all shark classes, compared to simpler models using temperature alone. Tiger shark range off the east coast of Australia is predicted to extend ~ 3.5° south towards the east coast of Tasmania, particularly for juvenile males. Our framework highlights the importance of combining long-term movement data with multi-factor habitat projections to identify heterogeneity within species when predicting consequences of climate change. Recognising intraspecific variability will improve conservation and management strategies and help anticipate broader ecosystem consequences of species redistribution due to ocean warming.

Highlights

Predator foraging behaviour is a complex interplay of biological traits including physiology, morphology, predation risk and life history (Huey and Pianka 1981; Preisser et al 2007) and is an important influence on the structure and Communicated by Yannis Papastamatiou.1 3 Vol.:(0123456789)Oecologia type, depth, reproduction, individual level of site fidelity and prey availability (Speed et al 2010; Espinoza et al 2021)
Sharks moved along the entire east coast of Australia from the Bass Straight to the Gulf of Carpentaria, and towards Papua New Guinea, the Solomon Islands, Tonga, and New Caledonia (Fig. 1; Appendix 1)
Female tiger shark southward dispersal was influenced by periods of warming temperatures, with effects observed for shark identification number (ID), tagging location and year (Table 2; Fig. 3)

Summary

Introduction

Depth, reproduction, individual level of site fidelity and prey availability (Speed et al 2010; Espinoza et al 2021). Changes in foraging behaviour occur throughout the lifespan of a predator as a consequence of ontogeny (Graeb et al 2005) and juveniles learning how to identify particular habitat features that improve feeding success (Grecian et al 2018). The physical properties of ecosystems tend to have an influence on predator behaviour and habitat use. Environmental gradients such as temperature, salinity, dissolved oxygen and barometric pressure, affect the patterns of space use of many predators (Block et al 2011; Schlaff et al 2014). Climate change is altering many of these oceanographic characteristics and influencing animal behaviour with increasing temperatures causing poleward shifts in species distributions leading to alterations in trophic structure (Vergés et al 2016). Marine predators can be more susceptible to fishing pressure as deoxygenation in deeper habitats compresses vertically available habitats (Vedor et al 2021)

Methods

Results

Conclusion