Ocean Biomedical UltraSound Lab

The Indo-Pacific bottlenose dolphin (Tursiops aduncus) is a critical species for coastal marine ecosystems; however, long-term monitoring remains challenging. Acoustic monitoring provides a noninvasive approach to studying dolphin populations, and in this study, signature whistles were identified from acoustic recordings collected around Jeju Island, South Korea. While conventional acoustic parameters, such as minimum and maximum frequency, duration, and frequency excursion, have been widely used to characterize dolphin whistle signals, they often are insufficient for capturing subtle within-whistle patterns critical for individual and population-level differentiation. To address this limitation, we introduce a novel symbolic contour encoding method termed DAS (Descent-Ascent-Static). Unlike traditional whole-whistle classification or scalar descriptor approaches, the DAS framework segments each whistle into discrete slope-based components, preserving fine-scale frequency modulation patterns. Comparative analyses revealed that the DAS-encoded features achieved clearer population separation in unsupervised clustering and principal component analyses, explaining nearly 90% of the variance compared with conventional parameters, which explains only approximately 60% of the variance. Additionally, we confirmed that more than half of the whistles detected were signature whistles, consistent with previous studies, and emphasized the importance of accounting for repeated signature whistle production to avoid statistical bias. This study represents the first report of signature whistles from the Jeju Island dolphin population and demonstrates that symbolic segment encoding offers a more biologically meaningful and statistically robust framework for population-level comparisons of dolphin vocal repertoires, with important implications for future ecological monitoring and conservation efforts aimed toward this species.

Amidst growing animal rights movements, the release of captive cetaceans, particularly killer whales and dolphins, into their natural environments has gained increasing support from activists due to ethical concerns. However, there is a notable lack of quantitative studies on the interactions between wild and captive dolphins during rehabilitation before release. This study assesses the rehabilitation process of captive dolphin during its stay in the sea pen using advanced surveillance techniques. Methods including CCTV, hydrophone monitoring, and drone observations were utilized to document interactions between rehabilitating and wild dolphins. A convolutional neural network-based detector for dolphin whistle sound was used to automatically detect the whistle from underwater sound recorded at the rehabilitation site, which significantly expedited the identification of wild dolphin encounters compared to traditional manual methods. This technology also facilitated synchronized analysis of underwater sounds, CCTV footage, and drone videos, providing comprehensive visual and acoustic observations of captive and wild dolphins during encounters. This research offers insights that can guide future dolphin rehabilitation monitoring and release strategies.

Blood viscosity is inversely proportionate with shear rate mainly due to red blood cell (RBC) aggregation under steady flow. However, this inverse relation cannot explain the spatiotemporal variation of RBC dynamics under pulsatile flow. This study aimed to clarify the relationship between hemodynamics and hemorheology based on a novel computational model that couples RBC dynamics with blood viscosity under pulsatile flow. By integrating both whole-blood experiments with ultrasound imaging and numerical simulations, the spatiotemporal variations of local hematocrit were shown to drive local variations of blood viscosity under pulsatile flow. The results suggest that the local parabolic distribution of high hematocrit is influenced by RBC aggregation and pulsatile flow characteristics, which in turn affect blood viscosity. Computational analysis supports that local blood viscosity increased in regions with elevated hematocrit during the acceleration phase of pulsatile flow. Local hematocrit and RBC dynamics play critical roles in influencing blood viscosity under pulsatile flow, highlighting the importance of incorporating hemorheological and hemodynamic factors. These are crucial for understanding large arterial flow and potentially enhancing diagnostic and therapeutic approaches for cardiovascular diseases.