Despite unpredictable weather, shorter autumn days, and navigation challenges, our experts collected valuable data on the distribution of the three cetacean species inhabiting Bulgarian Black Sea waters. Last week, a team from Green Balkans, along with colleagues from Burgas State University “Prof. Dr. Assen Zlatarov”, carried out another autumn research expedition to study cetaceans in the Black Sea.
On board the sailing yacht Kaliakria, the researchers surveyed Bulgarian territorial waters to collect up-to-date information on the occurrence and distribution of the three cetacean species inhabiting the Black Sea: the bottlenose dolphin (Tursiops truncatus ponticus), the common dolphin (Delphinus delphis ponticus), and the harbour porpoise (Phocoena phocoena relicta).
Autumn is a particularly interesting season for such research. Seasonal changes in water temperature, the distribution of fish schools, and the migratory movements of marine species can significantly influence the occurrence and behaviour of cetaceans. This year's expedition faced numerous challenges, including unpredictable weather conditions, limited daylight hours for observations, and increasingly complicated navigation conditions associated with ongoing military threats in the Black Sea. Nevertheless, the team completed a substantial part of the planned surveys.
During the expedition, a total of 403 km were covered in Bulgarian territorial waters, and 59 cetacean sightings were recorded, distributed as follows:
On board the sailing yacht Kaliakria, the researchers surveyed Bulgarian territorial waters to collect up-to-date information on the occurrence and distribution of the three cetacean species inhabiting the Black Sea: the bottlenose dolphin (Tursiops truncatus ponticus), the common dolphin (Delphinus delphis ponticus), and the harbour porpoise (Phocoena phocoena relicta).
Autumn is a particularly interesting season for such research. Seasonal changes in water temperature, the distribution of fish schools, and the migratory movements of marine species can significantly influence the occurrence and behaviour of cetaceans. This year's expedition faced numerous challenges, including unpredictable weather conditions, limited daylight hours for observations, and increasingly complicated navigation conditions associated with ongoing military threats in the Black Sea. Nevertheless, the team completed a substantial part of the planned surveys.
During the expedition, a total of 403 km were covered in Bulgarian territorial waters, and 59 cetacean sightings were recorded, distributed as follows:
- 25 sightings of bottlenose dolphins – the most frequently recorded species during the expedition;
- 20 sightings of common dolphins;
- 14 sightings of harbour porpoises – the smallest cetacean species inhabiting the Black Sea.
Of particular interest is the relatively lower number of harbour porpoise sightings. One possible hypothesis is that this distribution reflects the species' seasonal movements in late autumn, when individuals may shift their distribution in response to changing environmental conditions. Another possible explanation relates to the availability and spatial distribution of different fish species that form part of the cetaceans' diet. Bottlenose dolphins, common dolphins, and harbour porpoises have different feeding preferences and foraging strategies, which may help explain variations in their occurrence across the surveyed areas.
A preliminary spatial analysis of the collected data has identified two main areas with higher concentrations of cetacean sightings. The first covers the deeper parts of Bulgarian territorial waters south of Cape Kaliakra, while the second lies within the boundaries of the Ropotamo Special Area of Conservation, part of the European Natura 2000 ecological network. This observed spatial pattern is of particular interest for future research and may provide valuable insights into cetacean habitat preferences and the importance of these marine areas for their conservation.
It is important to note that the number of sightings does not directly reflect the abundance of individual species. To draw more robust conclusions, the results need to be analysed alongside survey effort, observation conditions, and data collected during previous expeditions. Each expedition adds another piece to the complex puzzle of life in the Black Sea. Regular cetacean monitoring across different seasons enables researchers to detect changes in species distribution, investigate their relationships with the marine environment, and identify potential threats to their survival.
For the tenth consecutive year, our team has successfully carried out more than one scientific expedition dedicated to studying cetaceans in the Black Sea. This continuity of research has been made possible thanks to the financial support of the Swiss foundation OceanCare, our longstanding and valued partner in efforts to study and protect the Black Sea ecosystem.
Each new expedition builds upon the knowledge gained over the years and contributes to a long-term scientific dataset that allows us to track changes in cetacean distribution and occurrence over time. This information is essential for gaining a better understanding of their ecological requirements, identifying threats, and developing effective conservation measures to protect these iconic inhabitants of the Black Sea.
Protecting the Black Sea begins with understanding the life it supports.
A preliminary spatial analysis of the collected data has identified two main areas with higher concentrations of cetacean sightings. The first covers the deeper parts of Bulgarian territorial waters south of Cape Kaliakra, while the second lies within the boundaries of the Ropotamo Special Area of Conservation, part of the European Natura 2000 ecological network. This observed spatial pattern is of particular interest for future research and may provide valuable insights into cetacean habitat preferences and the importance of these marine areas for their conservation.
It is important to note that the number of sightings does not directly reflect the abundance of individual species. To draw more robust conclusions, the results need to be analysed alongside survey effort, observation conditions, and data collected during previous expeditions. Each expedition adds another piece to the complex puzzle of life in the Black Sea. Regular cetacean monitoring across different seasons enables researchers to detect changes in species distribution, investigate their relationships with the marine environment, and identify potential threats to their survival.
For the tenth consecutive year, our team has successfully carried out more than one scientific expedition dedicated to studying cetaceans in the Black Sea. This continuity of research has been made possible thanks to the financial support of the Swiss foundation OceanCare, our longstanding and valued partner in efforts to study and protect the Black Sea ecosystem.
Each new expedition builds upon the knowledge gained over the years and contributes to a long-term scientific dataset that allows us to track changes in cetacean distribution and occurrence over time. This information is essential for gaining a better understanding of their ecological requirements, identifying threats, and developing effective conservation measures to protect these iconic inhabitants of the Black Sea.
Protecting the Black Sea begins with understanding the life it supports.
