A few decades after the common dolphins disappeared from the Adriatic Sea, larger groups are reappearing over the recent years. Researchers at the Blue World Institute recorded the largest ever-observed group of over 50 common dolphins near the islet of Mana, located near Kornati!

During regular monitoring of the bottlenose dolphins in the area of northern Dalmatia, carried out by the Blue World Institute in collaboration with the Nature Park “Telaščica” and the National Park “Kornati”, researchers came across a group of over 50 common dolphins (Delphinus delphis), a regionally extinct species that no longer resides in the Adriatic Sea!

„We encountered the group of common dolphins at about 2 NM west of the islet of Mana in the Kornati area. We spent a little more than two hours with them, collecting information on their behavior and taking photographs needed for photo identification. The fact that there were young dolphins and one newborn made us really happy! The dolphins occasionally swam at high speed and jumped, and it felt like we were on the ocean“says Tihana Vučur, a researcher at the Blue World Institute.

Her colleague, researcher Marko Radulović describes their encounter: “The dolphins were extremely friendly. They approached our boat few times and were bowriding. Moreover, when they turned away from the boat we saw them fishing for garfish near the surface. We also made some fantastic underwater shots!”

“The common dolphins, as their name suggests, were the most numerous dolphins in the Adriatic and Mediterranean Sea. Unfortunately, as well as the Mediterranean monk seal, the common dolphin is also considered a regionally extinct species in the Adriatic Sea because for some decades now there is no data on their permanent residence and reproduction, and the observations are rare and usually involve only a few individuals. That is why the encounter with this large group of common dolphins in the Adriatic is unique” says Dr. Nikolina Rako Gospić, director of the Blue World Institute´s science program.

The occasional appearance of a regionally extinct species in areas of former residence does not mean that the species has returned. However, the appearances that are more frequent may indicate that the species can again find the conditions necessary for at least a short-term stay in the area of ​​former residence. Researchers observed few smaller groups of about 20 to 30 common dolphins near the island of Dugi Otok during the summers of 2015 and 2016. The reappearance of this group, in which were also young dolphins, suggests that the species could return to the Adriatic one day.

Dr. Draško Holcer, senior curator of the Croatian Natural History Museum and president of the Blue World Institute, explored the reasons for disappearance of common dolphins from the Adriatic. “The beginning of the disappearance of the species from the Adriatic is linked to organized campaigns of killing and extermination because the dolphins were considered pests that destroy the fish stock and there was award for each killed dolphin. The extermination campaign escalated in the 1950s when almost 800 dolphins were killed mostly in the northern Adriatic area. The emergence of industrial fishing and ultimately overfishing, sea pollution (especially of northern Adriatic) and environmental changes caused by global warming and by the emergence of new species have led to the final disappearance of common dolphins from the Adriatic during the 1980s and 1990s. Unfortunately, the common dolphins are facing similar environmental problems throughout the Mediterranean. Today, this species is present in large number only in the Alboran Sea, the area around Malta and in some parts of the Aegean Sea” says Dr. Draško Holcer.

It is also interesting the fact that despite the common dolphins were once so numerous, there are almost no photos or videos documenting them. “The only old video of the Adriatic common dolphins we found was in the German state archive and it was taken in the vicinity of the island of Vis! The video clearly shows a smaller group of common dolphins as they follow a wooden boat sailing towards Komiža.” says Dr. Holcer. The common dolphin (Delphinus delphis) inhabits seas and oceans of moderate and tropical zones around the world. With a dark back and light belly, the common dolphin can be easily recognized by its distinctive yellow and white coloration on the side that looks like a reclining number eight. The common dolphin belongs to the group of smaller delphinids. The length of the body is usually up to 230 cm. They feed mainly on smaller blue fish and invertebrates. According to available data, the average life span of this species is around 30 years. Markings (cuts, scars, scratches and coloration) on the dolphin´s dorsal fin and body create a unique pattern that allows identification of each individual. By comparing the photographs that researchers are taking at various locations where they conduct the research, it is possible to determine whether there is migration of individuals between different areas. “During the sighting of the common dolphins, and for the purpose of photo identification, we made a large number of photographs that we will compare with photo catalogues from our colleagues in Greece and Italy. A possible positive identification would clarify a part of their behavior and migratory paths in the Mediterranean Sea! It is particularly interesting that, comparing the new photos with our catalogue, we found at least five dolphins observed also in 2016 around the island of Dugi Otok“, says Tihana Vučur. The population of Mediterranean common dolphins is endangered, the population number has been decreasing and its main cause are human activities. Threats include the lack of food due to overfishing, low frequency noise produced by merchant ships, tangling in fishing gear and the negative impact of pollution, especially chemical compounds that affect the immune system and cause reduced reproduction. Today, all dolphins and whales are legally protected and their hunt and harassment is forbidden, but despite the legal protection, the number of most species is decreasing.

We therefore invite all citizens to report their sightings of whales and dolphins in the Adriatic via e-mail (info@blue-world.org) or our Facebook page (www.facebook.com/blueworldinstitute), and to send us photos and videos, as they will help us gather the data needed to understand their life in the Adriatic Sea and their conservation.