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Regional populations ("subpopulations") of globally abundant species can be exposed to human impacts that threaten their viability. Given the value of cetacean subpopulations as evolutionary significant units, keystone and umbrella species, it is important to assess their conservation status separately and propose area‐specific conservation measures.We used a threat assessment process and applied IUCN Red List criteria to a regional population of common dolphins Delphinus delphis in the semi‐enclosed Gulf of Corinth, Greece. We compiled subpopulation‐specific information about abundance and trends, estimated the geographic range of the subpopulation (area of occupancy and extent of occurrence), and calculated the probability of extinction through stochastic modelling.The subpopulation qualified as Endangered according to criteria A (population size reduction over three generations) and B (geographic range), and as Critically Endangered under criteria C (population size and decline) and D (very small or restricted population). The probability of extinction was estimated to be ≥50% in three generations, qualifying the subpopulation as Critically Endangered under criterion E (quantitative analysis). We concluded that the subpopulation should be classified as Critically Endangered.Considering the high extinction risk faced by common dolphins in the Gulf of Corinth, we recommend that: (a) immediate action is taken to mitigate anthropogenic activities known or suspected to have a negative impact on cetaceans in the area (particularly commercial fishing); and (b) a marine protected area is established in the Gulf of Corinth as a management tool for enforcing conservation action and facilitating the recovery of common dolphins. [ABSTRACT FROM AUTHOR]

Understanding marine mammal distributions is essential for conservation, as it can help identify critical habitat where management action can be taken. The semi‐enclosed Gulf of Corinth, Greece, has been identified as an Important Marine Mammal Area by the International Union for Conservation of Nature (IUCN) Marine Mammal Protected Areas Task Force, based on the regular occurrence of odontocete populations. A 7‐year (2011–17) dataset of boat‐based surveys was used to model and predict the distribution of striped dolphins, Stenella coeruleoalba, common dolphins, Delphinus delphis, and common bottlenose dolphins, Tursiops truncatus, in the entire Gulf (2400 km2).Multiple geographic, bathymetric, oceanographic, and anthropogenic variables were incorporated in a combined generalized additive model and generalized estimation equation (GAM‐GEE) framework to describe dolphin occurrence and produce distribution maps.Modelling indicated that striped and common dolphins prefer deep waters (>300 m) in the central and southern part of the Gulf, whereas bottlenose dolphins prefer shallow waters (<300 m) and areas close to fish farms along the northern–central shore.Model‐based maps of the predicted distribution identified a preferred habitat encompassing most of the Gulf, also revealing: (i) hot spots of dolphin distribution covering about 40% of the Gulf's surface; (ii) an almost complete overlap of striped and common dolphin distribution, consistent with the hypothesis that common dolphins modified their habitat preferences to live in mixed species groups with striped dolphins; (iii) a clear partitioning of striped/common and bottlenose dolphin habitat; and (iv) the important role played by fish farms for bottlenose dolphins, consistent with studies conducted elsewhere in Greece.Evidence provided by this study calls for area‐specific and species‐specific management measures to mitigate anthropogenic impacts. [ABSTRACT FROM AUTHOR]

The Gulf of Corinth is a 2400-km² semi-enclosed inland system (a mediterraneus) in central Greece. Its continental shelf areas, steep bottom relief, and waters up to 500-900 m deep offer suitable habitat to neritic and pelagic species. We used photographic capture-recapture, distribution modelling, and direct observations to investigate the abundance, status, habitat preferences, movements, and group size of four odontocete species regularly observed in the Gulf, based on five years (2011-2015) of survey effort from small boats. Striped dolphins (Stenella coeruleoalba) are more abundant (1324 individuals, 95%CI 1158-1515) than was determined from previous estimates. Striped dolphins appear to be confined to the Gulf, where they favour deep and oligotrophic waters, and were encountered in single-species and mixed-species groups. Short-beaked common dolphins (Delphinus delphis) (22 individuals, 95%CI 16-31), individuals with intermediate pigmentation (possibly striped/common dolphin hybrids) (55, 95%CI 36-83), and a single Risso's dolphin (Grampus griseus) were only encountered in mixed-species groups with striped dolphins. Short-beaked common dolphins constitute a discrete conservation unit (subpopulation), and based on the current estimate, would qualify as Critically Endangered according to International Union for the Conservation of Nature (IUCN) Red List criteria. Common bottlenose dolphins (Tursiops truncatus) (39 animals, 95%CI 33-47) occur in single-species groups; they prefer continental shelf waters and areas near fish farms in the northern sector, and several animals appear to move into and out of the Gulf. Additionally, we contribute records of marine fauna and an assessment of the fishing fleet operating in the Gulf. Our study shows that the importance of this vulnerable marine environment has been underestimated, and management action must be taken to mitigate human impact and ensure long-term protection. [ABSTRACT FROM AUTHOR]

Capture-recapture methods relying on dorsal fin natural markings have never been applied successfully to striped dolphins, Stanley coeruleoalba, and were rarely used to assess abundance of short-beaked common dolphins, Delphinus delphis. We used digital photo-identification to obtain abundance estimates of striped and common dolphins living in mixed groups in the Gulf of Corinth, Greece. The proportion of either species was calculated based on the relative number of photographs of adult animals showing relevant portions of their body during conspicuous surfacings. Striped dolphins andcommon dolphins averaged 95.0% and 3.2% of all individuals, respectively. Animals showing intermediate pigmentation accounted for another 1.8%. Striped dolphin numbers were relatively high, with a point estimate of 835 animals (95% CI = 631–1,106). Common dolphins numbers were low (point estimate 28 animals; 95% CI = 11–73) and individuals were scattered within striped dolphin groups, indicating that thiscommon dolphin population may be nonviable. Within a semiclosed Gulf exposed to considerable anthropogenic impact, the future of both dolphin species is of concern due to their suspected geographic isolation and restricted extent of occurrence. Information provided here can be used to inform timely conservation efforts. [ABSTRACT FROM AUTHOR]