Temperature is one of the most influential drivers of physiological performance and behaviour in ectotherms, determining how these animals relate to their ecosystems and their ability to succeed in particular habitats. Here, we analysed the largest set of acceleration data compiled to date for elasmobranchs to examine the relationship between volitional activity and temperature in 252 individuals from 8 species. We calculated activation energies for the thermal performance response in each species and estimated optimum temperatures using an Arrhenius breakpoint analysis, subsequently fitting thermal performance curves to the activity data. Juveniles living in confined nursery habitats not only spent substantially more time above their optimum temperature and at the upper limits of their performance breadths compared to larger, less site-restricted animals, but also showed lower activation energies and broader performance curves. Species or life stages occupying confined habitats featured more generalist behavioural responses to temperature change, whereas wider ranging elasmobranchs were characterised by more specialist behavioural responses. The relationships between the estimated performance regimes and environmental temperature limits suggest that animals in confined habitats, including many juvenile elasmobranchs within nursery habitats, are likely to experience a reduction of performance under a warming climate, although their flatter thermal response will likely dampen this impact. The effect of warming on less site-restricted species is difficult to forecast since three of four species studied here did not reach their optimum temperature in the wild, although their specialist performance characteristics may indicate a more rapid decline should optimum temperatures be exceeded.
Bibliographical noteFunding Information:
Data collection was funded by National Science Foundation grants #1156141 and #1156145, NOAA Cooperative Research Program grants #NA13NMF4540056 and #NA15NMF4540102, NOAA Bycatch Reduction Program grants #NA13NMF4720274 and #NA14NMF4720320, a NOAA Species Recovery Grant to Florida (Sect. 6 Program) #NA13NMF4720047, the Australian Research Council (DECRA, Project number 150100321), the Fisheries Society of the British Isles, Australia Pacific Science Foundation, the Waitt Foundation, Western Australian Government State Natural Resource Management Program, and Murdoch University Strategic Research Funds.
Lemon and nurse shark data were collected at Bimini Biological Field Station with the help of S. Gruber, station managers, and many volunteers. Data collection for large coastal sharks was conducted with the help of J. Morris, H. Marshall, A. Andres, and numerous other staff and interns at Mote Marine Laboratory. Juvenile bull shark and largetooth sawfish data were collected by Murdoch University Team Sawfish, in collaboration with the Nyikina-Mangala Rangers. Smalltooth sawfish data were collected by the Florida Fish and Wildlife Conservation Commission’s Sawfish Program under NMFS ESA permit #15802. We thank C. White for assistance with statistical modelling. KOL was supported by an Australian Government Research Training Program Scholarship and the Forrest Research Foundation.
- Climate change
- Optimum temperature
- Performance breadth
- Performance curve