Population genetic structure of the short-beaked common dolphin from the Black Sea and the Turkish Straits System.

Our study aims to assess the population connectivity, evolutionary history, and conservation status of the short-beaked common dolphin in the Black Sea and Turkish Straits System (TSS). We also include DNA sequences from the Atlantic Ocean and the Mediterranean Sea to provide a regional perspective to our localized study. Analysis of 366 base pairs of mitochondrial DNA D-loop fragments from 37 samples collected from short-beaked common dolphins in the Black Sea, TSS, and Aegean Sea revealed 13 haplotypes, eight of which have not been previously reported. While analysis of samples archived on GenBank revealed 89 different haplotypes across the region. The haplotype network contains two main peripheral groups that include individuals from all locations. Haplotypes from the Atlantic Ocean are scattered across the network and no obvious population separation was detected. Some shared haplotypes potentially indicate multi-directional colonization events of the Mediterranean Sea from the eastern Atlantic Ocean. Moreover, some less widely distributed haplotypes suggest some level of more recent genetic connectivity through the Strait of Gibraltar and the TSS and point out the importance of these straits in the dispersal of short-beaked common dolphins. The haplotype and nucleotide diversity values were lower in the Black Sea, TSS, and western Mediterranean Sea when compared to the Atlantic Ocean, supporting the expansion of Atlantic populations into the Mediterranean and the Black Seas. Differentiation was observed between the Atlantic Ocean, and the Mediterranean Sea, TSS and the Black Sea based on Фst but not between Mediterranean and the Black Seas. For common dolphins, which have high dispersal potential, the protection of open seas and narrow seaways to enhance connectivity may be crucial.

Correction: The effects of marine traffic on the behaviour of Black Sea harbour porpoises (Phocoena phocoena relicta) within the Istanbul Strait, Turkey.

[This corrects the article DOI: 10.1371/journal.pone.0172970.].

The effects of marine traffic on the behaviour of Black Sea harbour porpoises (Phocoena phocoena relicta) within the Istanbul Strait, Turkey.

Marine traffic is threatening cetaceans on a local and global scale. The Istanbul Strait is one of the busiest waterways, with up to 2,500 vessels present daily. This is the first study to assess the magnitude of short- and long-term behavioural changes of the endangered Black Sea harbour porpoises (Phocoena phocoena relicta) in the presence of marine vessels within the Istanbul Strait. Markov chains were used to investigate the effect of vessel presence on the transition probability between behavioural states (diving, surface-feeding and travelling), and to quantify the effect on the behavioural budget and bout length (duration of time spent in a given state) of porpoises. Further, the changes on swimming directions of porpoises in relation to vessel speed and distance was investigated using generalized linear models. In vessel presence, porpoises were less likely to remain in a given behavioural state and instead more likely to switch to another state. Because of this, the bout length of all three behavioural states decreased significantly in the presence of vessels. The vessel effect was sufficiently large to alter the behavioural budget, with surface-feeding decreasing significantly in the presence of vessels. However, when taking into account the proportion of time that porpoises were exposed to vessels (i.e. 50%), the measured effect size was not large enough to significantly alter the animals' cumulative (diurnal) behavioural budget. Additionally, vessel speed and distance had a significant effect on the probability of porpoises showing a response in their swimming directions. The southern and middle sections of the Istanbul Strait, which have the heaviest marine traffic pressure, had the lowest porpoise sightings throughout the year. Conversely, northern sections that were exposed to a lesser degree of marine traffic hold the highest porpoise sightings. The effect shown in this study in combination with increasing human impacts within the northern sections should be considered carefully and species-specific conservation actions, including establishment of protected areas, should be put in place to prevent the long-term consequences of marine traffic on the Black Sea harbour porpoise population.