Tracking Dolphins in the Adriatic Sea

By Brianne Fagan, Earthwatch Intern

Morigenos - credit Tilen Genov - dolphins (22)After spending 12 hours on planes, trains, and automobiles, we arrived at the small, red-roofed, coastal city of Piran for our Tracking Dolphins in the Adriatic Sea expedition. We quickly loaded into the research boat for what Tilen, the lead investigator, called an “icebreaker” boat ride. Shortly after leaving the marina, our small team received a call from the bell tower where the land team was based with the location of dolphins. And just like that we were off, straight into the middle of the Gulf of Trieste, in the northern end of the Adriatic Sea.

A view of Tartini Square and Piran’s marina from the bell tower. A stage is present in the square to host the folklore festival occurring later in the week.

A view of Tartini Square and Piran’s marina from the bell tower. A stage is present in the square to host the folklore festival occurring later in the week.

After half an hour, we encountered our first dolphins who warmly welcomed us to Slovenia with a series of acrobatic jumps and splashes. It was the “evening group,” as the researchers call them – a large group of dolphins that hang out in the Gulf in the later hours of the day. Tilen snapped photograph after photograph of them while the rest of us called out when another one appeared. This wasn’t a difficult task since the dolphins had surrounded us. Amazingly, Tilen began introducing us to them, “That’s Moni right there! Hello, Moni!” or, “That’s Kat at 3 o’clock with her calf!” This went on for about two hours until the sun began to set. It was then that we broke contact with the dolphins and headed back to Piran. It was also then that I was able to take a minute to absorb the last few hours. I was in the middle of the Adriatic Sea, on a boat with a group of strangers, tracking dolphins.

Some of the evening group is spotted jumping and playing in the distance.

Some of the evening group is spotted jumping and playing in the distance.

Morigenos and the Slovenian Dolphin Project

Common bottlenose dolphins are a flagship species not only because of their charismatic personalities, but also because of the role they play within their ecosystem. Dolphins are top predators, and as such, serve as an indicator species. This means that a decrease in dolphin health may be indicative of a change to their ecosystem. Morigenos, the Slovenian Marine Mammal Society located in Piran, established a Slovenian Dolphin Project in 2002 in order to monitor the local dolphin population. Before the launch of this project, there was no evidence or information pertaining to dolphins in the region. In fact, marine biologists did not even know that dolphins even existed in the area!

The researchers are able to identify individual dolphins based on the markings and shape of their dorsal fins which, like fingerprints, are distinct from one another. Once they have photographs of the fins, they add them to a photo-ID catalogue and assign them a name. This allows the team to gather information on population size and structure, feeding and social behavior, site fidelity, diet, reproductive rates, survival rates, and various other parameters that can indicate population health.

Dorsal fins have unique shapes, pigmentation, and markings that dolphins acquire throughout their lifetime. ©Morigenos

Dorsal fins have unique shapes, pigmentation, and markings that dolphins acquire throughout their lifetime. ©Morigenos

The Loss of a Dolphin

An assistant, Jan, surveys the water from the bell tower using Big Eyes - an extremely strong pair of binoculars.

An assistant, Jan, surveys the water from the bell tower using Big Eyes – an extremely strong pair of binoculars.

About a week into the expedition we were scanning for dolphins from the bell tower when Ana, a lead investigator, noticed something suspicious and called Tilen over to take a look. It was an unwanted and dreaded sight for the team – a dead dolphin, bloated and floating on top of the water.

In these situations, the team will collect the animal and contact their veterinary partner who will later conduct a necropsy to determine the cause of death, if possible. Sometimes the dolphin can be identified with its dorsal fin, unless the fin is no longer viable or the dolphin is not in the ID catalogue. The dorsal fin of this dolphin, unfortunately, was too deteriorated to allow identification.

Although the dolphin may have died of natural causes, there are many human-induced risks to dolphins that may result in decreased health or even death. Some of the most common risks are related to boat traffic, toxins, and bycatch. Boat traffic is rarely the direct cause of death for a dolphin, as dolphins are agile and can usually avoid boat strikes. The real problem is that some boats transmit sound at the same frequencies that dolphins use to communicate, resulting in unsuccessful hunting or general confusion. Toxins, however, can directly impact health. High levels of polychlorinated biphenyls (PCBs), for example, have been found in the blubber of the Slovenian dolphin population, resulting in decreased reproductive success and weakened immune systems. Bycatch, although highly detrimental in some areas of the world, is fortunately a rare occurrence in the area.

Morigenos - credit Ana Hace - dolphins (3)

When Ana and I returned from fueling the boat one day, a couple of local fishermen invited us to join them at a local café. As Ana and the fishermen discussed their genuine fears and hopes for the future of Slovenian waters, I sat back and took in the view, appreciated my company, and reflected on the expedition. Although my time in Piran was over, after all of the field work, the unrelenting heat, the countless hours spent surveying for dolphins, I could safely say that I had gathered a sense of the importance and difficulty of such a study, as well as a true appreciation for the life of a dolphin researcher.

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