The shallow continental shelf area of the Northern Adriatic hosts an estimated 6,000 Vulnerable Mediterranean common bottlenose dolphins (Tursiops truncatus). Genetic evidence reveals a fine-scale genetic structure, with differentiation between north and south-central areas, as well as between the west and east coasts. In addition, evidence suggests that the Gulf of Trieste hosts another unit, with significant genetic differentiation from the rest of the Adriatic Sea. Residency patterns have been identified along coastal areas of the eastern Adriatic with at least three distinct local communities across the Gulf of Trieste, the Kvarnerić, and north Dalmatia. Three EU Natura 2000 Special Areas of Conservation have been designated for common bottlenose dolphins in Croatian waters.
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
The IUCN classifies the Mediterranean subpopulation of common bottlenose dolphin as Vulnerable on Red list of Threatened Species. These animals live in a region of high anthropogenic use. The continental shelf of northern Adriatic is one of the most heavily exploited area for fisheries (trawling, shells dredging, pelagic trawling and purse-seining, set nets, longlines), shipping, and pollution in the Mediterranean. In addition, tourism and recreational traffic is increasing during the summer months, causing physical disturbance and increased noise levels.
Criterion B: Distribution and Abundance
Sub-criterion B2: Aggregations
Aerial surveys in summers of 2010 and 2013 produced high estimates of abundance for common bottlenose dolphin in the area. Estimated abundance of Tursiops truncatus based on 2010 aerial survey, corrected for availability and perception bias (group size, time on surface), in the shallow continental shelf area of northern Adriatic was 6,577 (CV 20,3%; 95% CI 4,412-9,805). The high abundance has been further confirmed with predicted abundance using surface density models.
Criterion C: Key Life Cycle Activities
Sub-criterion C1: Reproductive Areas
Species is present year-round in the area, hence reproduction takes place within the area. Apart from aerial surveys and dedicated long-term photo-identification research surveys confirming observations of young animals, year-round monitoring of bycatch in midwater pair trawling fleet of Italy, operating in the northern Adriatic between 2006-2013 produced thousands of observations of different group sizes of T. truncatus in the whole northern Adriatic basin throughout the year. Numerous observations of newborns, calves and juvenile animals confirm that further.
Criterion D: Special Attributes
Sub-criterion D1: Distinctiveness
Tursiops truncatus seems almost uniformly distributed throughout the Adriatic basin. However, genetic evidence rejected the hypothesis of a single stock. Pairwise estimates of genetic differentiation at 17 microsatellite loci, and mitochondrial DNA, revealed diverse levels of genetic differentiation among the Adriatic Sea. The results suggest that bottlenose dolphin exhibits population structures that correspond well to the main Adriatic basins, and that the genetic differentiation is not correlated to geographic distances. At a nuclear level, common bottlenose dolphins revealed a fine-scale genetic structure, showing a differentiation between north and central-south areas, as well as between the west and east coast. In addition, individuals from the Gulf of Trieste seem to belong to a group of animals significantly differentiated from the rest of the Adriatic Sea.
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