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The Istanbul Strait (Bosphorus) is a part of the Turkish Straits System, connecting the Aegean Sea and the Black Sea. There are three cetacean species in the Strait, namely the harbour porpoise (Phocoena phocoena), the common dolphin (Delphinus delphis), and the bottlenose dolphin (Tursiops truncatus). To monitor the presence of the cetaceans, a fixed stereo passive acoustic monitoring system (A-tag) was deployed in the middle of the Strait from July 2009 to September 2010. In total 26,814 click trains were detected. Presence, direction and inter-click intervals of phonating cetaceans were measured. Most click trains were detected during the night time. Diel presence pattern was prominent in March and April. In spring, the cetaceans were concentrated in one specific direction from the fixed monitoring system. In contrast, they were found in all directions for the rest of the year. Short range sonar (inter-click intervals (ICIs) less than 50 ms) was commonly detected in spring. During the rest of the year ICIs could reach up to 150 ms. All these findings suggest that they were feeding or socializing in spring and mostly travelling in the other seasons. It is well known that pelagic fish such as sprat and bluefish start their migration from the Aegean Sea to the Black Sea in spring. This study suggests that the cetaceans use the middle part of the Strait for feeding on the pelagic fish in spring when the fish migration has just started.

Stomach contents of six striped dolphins taken as by-catch in the swordfish fishery in the eastern Mediterranean Sea off the Turkish coast were examined. In total, 29 taxa were identified to species or family and 1777 individual food items (1394 bony fishes, 289 cephalopods, 94 crustaceans) were counted.Diaphusspp. andCeratoscopelus maderensiswere the most remarkable ones, as they accounted for 70.45% of the total number of fishes.Onychoteuthis banksii, on the other hand, was the only cephalopod species found in all stomach content analyses and represented 38.06% of the total number of cephalopods. Bony fish species:Myctophum punctatum, Notoscopelus elongatus, Electrona risso, Sudis hyalina,Moridae sp., Phycidae sp., Sternoptychidae sp. and cephalopods:Pterygioteuthis giardiandChtenopteryx siculawere reported the first time in the stomach contents of striped dolphin in the Mediterranean Sea.

We investigated the presence and diversity of cetaceans in the Mediterranean Sea, analysing the data collected by 32 different research units, over a period of 15 years (2004–2018), and shared on the common web-GIS platform named Intercet. We used the encounter rate, the species prevalence, and the Shannon diversity index as parameters for data analysis. The results show that cetacean diversity, in the context of the Mediterranean basin, is generally quite low when compared with the eastern Atlantic, as few species, namely the striped dolphin, the bottlenose dolphin, the fin whale, and the sperm whale, dominate over all the others. However, some areas, such as the Alboran Sea or the north-western Mediterranean Sea, which includes the Pelagos Sanctuary (the Specially Protected Area of Mediterranean Interest located in the northern portion of the western basin), show higher levels of diversity and should be considered hotspots to be preserved. Primary production and seabed profile seem to be the two main drivers influencing the presence and distribution of cetaceans, with the highest levels of diversity observed in areas characterized by high levels of primary production and high bathymetric variability and gradient. This collective work underlines the importance of data sharing to deepen our knowledge on marine fauna at the scale of the whole Mediterranean Sea and encourages greater efforts in the networking process, also to accomplish the requirements of the Marine Strategy Framework Directive, with particular reference to Descriptor 1: biological diversity is maintained.

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An adult, female harbour porpoise (Phocoena phocoena relicta) was found stranded on the southern Aegean Sea coast of Turkey. Thirteen holes made by copepods were observed on the lateral sides of the porpoise. The copepods were identified as Pennella balaenopterae, based on the morphological characteristics and measurement. Tissue samples were collected from embedded parts of parasites, histopathologically examined and panniculitis findings were observed. Although this parasite copepod had been reported on several marine mammals, this is the first report in the harbour porpoise, and in the Aegean Sea.

Genetic population structure of geographically isolated endangered Black Sea harbor porpoise (Phocoena phocoena relicta) is little known in Turkish waters, especially in the Turkish Straits System (TSS- Marmara Sea, Bosphorus and Dardanelles), which connects the Black Sea and the Aegean Sea. Mitochondrial DNA sequences of 70 new individuals sampled in the Turkish Black Sea, TSS and Aegean Sea, revealed five new haplotypes from the Black Sea. The findings support the idea that harbor porpoises from the Black Sea dispersed into the Aegean through the TSS. Considering signatures of population expansion, all subpopulations showed a signature of population expansion. The network data and the Фst calculations indicated that the Marmara Sea subpopulation was significantly differentiated from all of the other subpopulations, and supports the notion of its isolated. The finding of a potential management unit (MU) within an already heavily impacted subpopulation as a whole suggests that the individuals of P. p. relicta inhabiting the Marmara Sea require a very rigorous conservation strategy to ensure the survival of this subpopulation, represented by its unique haplotype.