WHALES AND DOLPHINS OF THE ADRIATIC SEA: WHAT DO WE KNOW ABOUT THEM?

Morigenos participated in a new review study on whales and dolphins of the Adriatic Sea, published last week. In this comprehensive study, scientists review and summarise the existing knowledge on Adriatic cetaceans and provide guidelines for their long-term conservation. The study was published in the scientific journal Acta Adriatica.
In this new review, scientists carried out a very comprehensive review of the existing literature on whales and dolphins in the Adriatic Sea, and synthesised the findings of different studies. They looked at all aspects of various species of cetaceans living in the region: their distribution, abundance, genetic structure, behaviour, threats, etc. Reviews represent a synthesis of the knowledge generated by the various individual studies.
The published review shows the multifaceted status of Adriatic cetaceans. On the one hand, the diversity of cetacean species in the Adriatic is greater than many people probably imagine: five species live here regularly, and two more occur occasionally. Whales and dolphins are predators at the top of the marine food web and therefore play an important role in marine ecosystems. Their presence in the Adriatic Sea is a good sign in this respect. On the other hand, the Adriatic Sea is one of the most human-impacted areas in the Mediterranean Sea, exposed to many stressors that have a negative impact on the state of marine ecosystems and directly threaten Adriatic cetaceans.
So, what whales and dolphins live in the Adriatic? The most abundant species is the striped dolphin (Stenella coeruleoalba), which lives in the deep southern Adriatic (relatively rarely recorded in the Gulf of Trieste and Slovenia). The second most abundant species, which is also the most widespread throughout the Adriatic, is the bottlenose dolphin (Tursiops truncatus), which also lives in the Gulf of Trieste and Slovenian waters, and which has been studied by Morigenos researchers for more than 20 years. The common dolphin (Delphinus delphis) used to be common in the Adriatic, but is now comparatively rare. In the southern Adriatic, the Risso’s dolphin (Grampus griseus) and the Cuvier’s beaked whale (Ziphius cavirostris) are also present in smaller numbers. The latter is the world’s absolute diving record holder, as it can dive down to 3,000 m and stay underwater for more than three hours. The fin whale (Balaenoptera physalus), which occasionally visits the Gulf of Trieste, and the sperm whale (Physeter macrocephalus) are also occasionally seen, while other species are extremely rare in the Adriatic Sea. This includes the humpback whale (Megaptera novaeangliae), which spent two months in Slovenian waters in 2009.
Despite this relative diversity, the status of cetaceans in the Adriatic is worse today than it was a few decades ago. Between the 19th and mid-20th century, thousands of dolphins were deliberately killed in the Adriatic, leading, among other things, to the near disappearance of the common dolphin. Today, Adriatic cetaceans face many threats, including the combined effects of habitat loss and degradation, prey depletion, incidental mortality in fishing gear, anthropogenic noise, marine litter, chemical pollution and climate change. The Adriatic is a particularly vulnerable ecosystem due to its semi-enclosed nature and relative shallowness, and it is also the most heavily trawled sea in the world.
The lead author Dr Giovanni Bearzi reports: “In the past, dolphins were regarded as pests and the practice of killing them was common and widespread, largely as an attempt to reduce conflict with fisheries. In the Adriatic Sea, dolphin extermination campaigns were promoted by the authorities responsible for fisheries management, and these killings were carried out for more than a century, until as recently as the 1960s.”
“Today we know that large predators such as whales, dolphins and sharks aren’t pests, but instead play a very important role in the marine ecosystems” said Dr Tilen Genov, president of Morigenos and lecturer at the University of Primorska. “The data are clear: if we want a healthy and plentiful sea, which we humans also depend on, we need healthy populations of large marine predators.”
The authors believe that this new review will serve as a useful reference for researchers in the region, students, decision-makers and all those interested in Adriatic cetaceans, and will also provide a useful baseline for future research.
The review paper is available here: https://acta.izor.hr/ojs/index.php/acta/article/view/1422.