Date

Summer 2025

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

Climate change has shifted species' distributional ranges in many marine and terrestrial systems. For marine species, those shifts in ranges associated with ocean warming are often poleward or into deeper waters. Juvenile white sharks (Carcharodon carcharias) are one such species, having exhibited a 270 km range shift of the cold edge of their thermal range extending northward to the Monterey Bay. However, little is known about the fine-scale habitat selection of marine organisms at the cold edge of their shifting range and how localized thermal gradients or warm pools may permit persistence in these newly inhabited locations. The Monterey Bay provides a unique study system with high spatial variability of environmental conditions, and a range-shifting endothermic predator, the white shark, that is highly mobile and known to be sensitive to ambient temperatures. This research investigates fine-scale habitat selection by juvenile white sharks in this dynamic system at the submesoscale (1-10 km) using remote sensing, aerial surveys, and acoustic telemetry to link spatial and temporal patterns of site occupancy with environmental conditions. Results indicate that increases in sea surface temperature (SST) and K490 (light attenuation coefficient proxy for turbidity) are significantly positively associated with juvenile white shark abundance assessed via remote sensing. However, the positive response to temperatures at the surface contrasts with those at depth exhibited by acoustic telemetry techniques, suggesting diverging behaviors. As juvenile white sharks extend their range northward, they may be utilizing pockets of warm surface water, enhanced by increased turbidity, as refuges in regionally cooler, less suitable areas. While at-depth temperature trends, paired with higher residence times observed at subsurface sites between the hours of 9:00 PM and 7:00 AM, indicate potential foraging behavior offshore before returning to coastal surface waters to rewarm. Understanding range shifts of predators is important as their presence in novel locations can result in changes in predator-prey interactions and new top-down effects on local ecosystems.

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