Seasonal abundance estimates of cetaceans in the southern Black Sea (Sinop), Türkiye

The availability of reliable information on the abundance and distribution of threatened species is fundamental to evaluating their conservation status and taking the necessary measures to implement effective management. The seasonal abundance and distribution of cetaceans in the Sinop region, one of the essential fishing areas of the Black Sea, were estimated with line-transect data. Dedicated boat-based visual observations were conducted in four seasons between May 2019 and March 2020. Average estimates of abundance in the region over all seasons were 1,058 individuals for Black Sea harbor porpoises (Phocoena phocoena relicta; CV = 19.25%, 95% CI[725, 1,542]), 188 individuals for Black Sea bottlenose dolphins (Tursiops truncatus ponticus; CV = 21.67%, 95% CI[123, 289]), and 311 individuals for Black Sea common dolphin (Delphinus delphis ponticus; CV = 16.77%, 95% CI[123, 427]). The highest estimates for all three species were obtained in the spring. Harbor porpoises and bottlenose dolphins were present in the study area throughout the year, while common dolphins left the region in winter. These findings offer valuable insights that can guide and inform future conservation strategies, aligning with national and international frameworks for the protection of these cetacean species.