Why sharks gather: seasonal residency and thermal responses at coastal infrastructure in the eastern Mediterranean Sea

The eastern Mediterranean Sea is among the warmest and most oligotrophic marine regions globally. Shark aggregations at coastal infrastructure in this basin offer an accessible setting for empirically examining behaviour under environmental conditions relevant to climate change projections. We used acoustic telemetry to monitor 58 dusky and sandbar sharks ( Carcharhinus obscurus , n = 35; C . plumbeus , n = 23) across coastal infrastructure and natural habitats in Israel. Integrating movement data with core body-temperature records, we quantified site fidelity, residency, and thermal dynamics at multiple temporal scales. Our results reveal low interannual return rates to the broader region but pronounced within-season residency at the Orot-Rabin station. Visit timing and diel activity patterns suggest temporally structured use of the site. Core body temperature increased progressively during visits and exceeded ambient seawater temperature, consistent with thermoregulation. Collectively, these findings indicate that fine-scale environmental heterogeneity may shape behavioural strategies that support physiological functions and social processes, including metabolic and muscular performance, reproduction, or information transfer within a warm, oligotrophic system. However, attraction to coastal infrastructure may also increase exposure to anthropogenic threats, suggesting a potential trade-off between energetic benefits and long-term population viability.