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Bottlenose dolphins off Slovenia

 

Knowledge on cetaceans inhabiting Slovenian waters was quite poor until recently. In 2002, Morigenos initiated a long-term project on the ecology, status and conservation of bottlenose dolphins in Slovenian and adjacent waters. This led to the finding that the area is regularly used by a small local population of bottlenose dolphins, which appear to be resident.

 

Morigenos researchers following bottlenose dolphins off the coast of Slovenia. Photo © Morigenos.

 

The bottlenose dolphin is the only regularly encountered cetacean in the area. Striped dolphins may be sighted occasionally, while Risso's dolphins, fin whales and other cetaceans rarely occur.

About 100 bottlenose dolphins have been photo-identified so far, although some have been encountered only once or twice. About 30-40 individuals are sighted regularly. These animals display a high degree of site fidelity. Observations of feeding behaviour suggest that Slovenian waters may be an important feeding ground for this local population.

Mothers with calves have been observed every year, suggesting that the area could also serve as a breeding and/or nursing ground. As the Slovenian coastline is very short (46 km) and dolphins are highly mobile animals, they regularly move across national borders into neighbouring Italian and Croatian waters. For this reason, research is transboundary.

A high degree of interactions with fisheries (particularly Slovenian pair trawlers) was recorded. Pair trawlers appear to attract dolphins and may influence their distribution and movements.

 

A bottlenose dolphins behind a trawler off Slovenia. Photo © Morigenos.

 

Boat traffic resulting from tourism may negatively affect dolphins in summer months, displacing them from coastal areas. Ongoing research should provide information on the actual impact of pleasure boating.

Comparisons with bottlenose dolphins photo-identified in the Cres-Losinj archipelago, Croatia, suggest low levels of intermixing.

The coastal waters of Slovenia are exposed to intensive fishing, coastal development, chemical and noise pollution. Therefore, local bottlenose dolphins are exposed to threats that need to be taken into account to define appropriate management strategies.

 

Cetacean Alliance investigators:

For more information, see:

Bearzi G., Holcer D., Notarbartolo di Sciara G. 2004. The role of historical dolphin takes and habitat degradation in shaping the present status of northern Adriatic cetaceans. Aquatic Conservation: Marine and Freshwater Ecosystems 14:363-379. (212 Kb)

Genov T., Kotnjek P., Lesjak J., Hace A., Fortuna C.M. 2008. Bottlenose dolphins (Tursiops truncatus) in Slovenian and adjacent waters (northern Adriatic Sea). Annales (Series Historia Naturalis)18(2):227-244. (1.1 Mb)