Behavioral response of a mobile marine predator to environmental variables differs across ecoregions

Abstract

Animal movement and habitat selection are in part a response to landscape heterogeneity. Many studies of movement and habitat selection necessarily use environmental covariates that are readily available over large‐scales, which are assumed representative of functional habitat features such as resource availability. For widely distributed species, response to such covariates may not be consistent across ecosystems, as response to any specific covariate is driven by its biological relevance within the context of each ecosystem. Thus, the study of any widely distributed species within a limited geographic region may provide inferences that are not widely generalizable. Our goal was to evaluate the response of a marine predator to a suite of environmental covariates across a wide ecological gradient. We identified two behavioral states (resident and transient) in the movements of shortfin mako sharks Isurus oxyrinchus tracked via satellite telemetry in two regions of the western North Atlantic Ocean: the tropical Caribbean/Gulf of Mexico marginal sea (CGM), and the temperate waters of the open western Atlantic Ocean (OWA). We compared patterns of resident behavior between regions, and modeled relationships between oceanographic variables and resident behavior. We tracked 39 sharks during 2013–2015. Resident behavior was associated with shallow, continental shelf and slope waters in both regions. In the OWA resident behavior was associated with low sea surface temperature and high primary productivity, however, sharks exhibited no response to either variable in the CGM. There was a negative relationship between sea‐surface height gradient (a proxy for oceanic fronts) and resident behavior in the OWA, and a positive relationship in the CGM. Our observations likely reflect shark responses to regional variability in factors responsible for the distribution and availability of prey. Our study illustrates the importance of studying widely distributed species in a consistent manner over large spatial scales.

New Insights Into the Seasonal Movement Patterns of Shortfin Mako Sharks in the Gulf of Mexico

“…While most individuals in this study were mature, previous studies on juveniles have also reported similar habitat use patterns between open-ocean and continental shelf use (Rogers et al, 2015;Vaudo et al, 2017;Byrne et al, 2019). Juveniles tagged off the Yucatan Peninsula demonstrated high residency to the eastern edge of the Campeche Bank (Vaudo et al, 2017;Byrne et al, 2019), and juveniles tagged off the coast of Australia exhibited high site fidelity to the mid-outer continental shelf near the Great Australian Bight (Rogers et al, 2015). This shallower, continental shelf habitat is likely attractive due to the abundance and variety of prey available compared to open-ocean habitats (Byrne et al, 2019).…”

“…This coastal, nearshore habitat use, which has also been reported in previous studies (Francis et al, 2019), exposes this generally pelagic species to shore-based fisheries. While most individuals in this study were mature, previous studies on juveniles have also reported similar habitat use patterns between open-ocean and continental shelf use (Rogers et al, 2015;Vaudo et al, 2017;Byrne et al, 2019). Juveniles tagged off the Yucatan Peninsula demonstrated high residency to the eastern edge of the Campeche Bank (Vaudo et al, 2017;Byrne et al, 2019), and juveniles tagged off the coast of Australia exhibited high site fidelity to the mid-outer continental shelf near the Great Australian Bight (Rogers et al, 2015).…”

Seasonal Occurrence, Horizontal Movements, and Habitat Use Patterns of Whale Sharks (Rhincodon typus) in the Gulf of Mexico

“…where m = month (1-12; Byrne et al, 2019). To account for individual variation, we included shark ID as a random effect.…”

Unusually Paced Life History Strategies of Marine Megafauna Drive Atypical Sensitivities to Environmental Variability

“…With ongoing climate change impacting ecosystems worldwide, an urgent question is how the subtly different life history strategies of mobulids, carcharhinids and cheloniids buffer or intensify their demographic responses to climate change induced shifts in environmental stochasticity ( Table 1; Carr et al, 1978;Morreale et al, 1982;Limpus and Reed, 1985;Janzen, 1994;Hawkes et al, 2009;Moffitt et al, 2015;Marn et al, 2017a). This requires in depth understanding of their demographic responses to shifts in environmental autocorrelation and good environment frequency (Table 1), and the physiological processes that drive these (Marn et al, 2017b), which is all essential for the successful conservation management of marine megafauna (Cortés, 2002;Oh et al, 2017;Byrne et al, 2019).…”