Unusual mass mortality of harbour porpoises on the coast of the western Black Sea (Bulgaria and Turkey) in summer 2016
31th Annual Conference of the European Cetacean Society, Kobenhavn, Danimarka, 1 - 03 Mayıs 2017, ss.297, (Özet Bildiri)
- Yayın Türü: Bildiri / Özet Bildiri
- Basıldığı Şehir: Kobenhavn
- Basıldığı Ülke: Danimarka
- Sayfa Sayıları: ss.297
- Dokuz Eylül Üniversitesi Adresli: Hayır
Özet
Between late June and late August 2016, an unusual mass mortality of harbour porpoises (Phocoena phocoena) relicta was observed on the western Black Sea coasts of Turkey and Bulgaria. The information were collected by stranding surveys, İÜ-TUDAV Cetacean Stranding Network, media (newspaper, TV, online news), social media, environmental authorities (RIOEW-Burgas), as well as the website and app of BlackSeaWatch Project. In total 443 stranded cetaceans (435 harbour porpoises, five common dolphins, two bottlenose dolphins, one unidentified) were reported in Turkey on the coastline of approximately 300km and 234 (218 harbour porpoises, one common dolphin, 14 bottlenose dolphins and one unidentified) along the southern Bulgarian coast of 238 km. In Bulgaria the number goes up to 361 if the cases reported by citizens but not confirmed by experts are included. The peak was reached in July in both Bulgaria and Turkey. Highest cetacean stranding rate was recorded (7.1 ind./km) in Turkey since 2003 by regular monitoring surveys compared to normal rates ranging between 0.1 and 1.1 (ind./km) in summer months. Most of them (about 90%) were neonates (<1 year of age), around 70cm in body length. Almost all specimens were at the advanced stage of decomposition (stage 4-5), which made it impossible to determine the reason for such mortality. The carcases, however, were mainly of very young animals (<1 year of age) and not of adults. This indicates that potential causes such as bycatch, biotoxin, infectious diseases, starvation, acoustic trauma, heavy metals and chemical contamination are unlikely causes. Based on the available stranding rate of carcases, we assume thousands of juveniles died during this mortality event in western Black Sea coast. Such damage to an already threatened population of Black Sea harbour porpoises needs to be monitored and taken into consideration for elaborating the conservation plan.