Limited knowledge about the site fidelity of bottlenose dolphins along the southwestern Black Sea coast presents a gap in understanding their habitat use and movement patterns. To address this, a boat-based surveys (March 2019-November 2024) were conducted in Zonguldak province resulting in 99 sightings, and photo-identification data were collected for the first time in this region. The occurrence, group dynamics and site fidelity patterns were assessed through a capture-recapture statistical method. The 185 identified individuals were grouped into clusters using an agglomerative hierarchical cluster analysis. Results showed that dolphins were mostly encountered in shallow waters in depths below 100 m (77% of sightings) and were present year-round. Group sizes varied across the seasons, with the largest sizes observed during winter (p < 0.05). Bottlenose dolphin groups that included calves were larger (median = 5) than those without calves (median = 2). Most of the identified dolphins (149 out of 185) were observed using the area only once over the study period, indicating a low level of site fidelity; only 36 individuals were considered temporary visitors with varying degrees of return to the study area. The year-round presence of dolphins in combination with temporal fluctuations in group size and the occurrence of mother-calf groups emphasizes the need for efficient conservation management. The predominance of transient individuals further suggests that conservation efforts should extend beyond the local scale to investigate migration corridors between neighbouring regions.