Fine-scale behavior and habitat use of the endangered smalltooth sawfish (Pristis pectinata): insights from accelerometry

Determining movement, behavior, and activity patterns is of central importance to conservation efforts for threatened and endangered species because this knowledge is crucial for prioritizing management actions. In this study, we used acceleration data loggers (ADLs) concurrently with passive acoustic monitoring to examine behavior, activity patterns, and habi¬tat use of juvenile smalltooth sawfish (Pristis pectinata) in a Florida nursery. Data from the ADLs indicate that small¬ tooth sawfish were more active and that more burst events indicative of foraging occurred during the evening and night than during the day. Smalltooth sawfish were also most active at depths <1 m and during low tides. The locations of individuals derived from acoustic mon¬itoring techniques indicate that they were less active while in mangrove creek habitats and were more active and more likely to engage in burst activity in habitats within the main stem of the Peace River. This study is the first one to deploy ADLs on smalltooth sawfish, and results describe their fine scale activity and behavior, clarifying patterns of habitat use by this endangered species in one of their few remaining nurseries

Thermal performance responses in free-ranging elasmobranchs depend on habitat use and body size

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