Citizen-science records document two young great white sharks in the Eastern Adriatic

Two citizen-science records from fishers in Croatia and Montenegro document young-of-the-year great white sharks (Carcharodon carcharias) in the Eastern Adriatic Sea, adding evidence for the area’s potential importance to the species without establishing a nursery habitat. The observational study, published in Acta Ichthyologica et Piscatoria, describes one shark caught in August 2018 and another caught and released in June 2025.

The researchers received photographs from the fishers and contacted them directly for information about the catches. The images were examined with Google Reverse Image Search to check that they had not previously been published elsewhere. Species identification was based on visible diagnostic characters, including a moderately long, bluntly conical snout, five long gill slits, relatively large dark eyes, long pectoral fins, narrow triangular teeth, a sharp change from grey-brown dorsal to white ventral coloration, and a lunate caudal fin with a subterminal notch. The absence of a secondary caudal keel distinguished the sharks from the porbeagle, Lamna nasus. A maximum total length of 1.75 metres was used to classify a great white shark as young-of-the-year.

In the Croatian record, the Institute of Oceanography and Fisheries in Split received photographs in August 2018 from a fisherman who had sought identification of an elasmobranch. The shark had been caught six nautical miles south of Glavat Island in a gillnet deployed at approximately 125 metres depth to target large demersal fish. It was dead when the fishing gear was retrieved, and the specimen had already been partially processed.

The fisherman estimated the Croatian animal’s total length at 175 centimetres and total weight at 45 kilograms. A hook was embedded in its upper jaw, which the researchers considered likely to have remained from an earlier capture. The available photographs documented the head, jaws, teeth, caudal peduncle and a severed caudal fin, allowing the researchers to assess features used in the species identification. Because the animal was dead and partly processed when documented, the study did not involve a standardized examination of a living or intact specimen.

The second observation occurred on 23 June 2025 off Montenegro. Staff from the Institute of Marine Biology at the University of Montenegro received photographs from a fisherman who had previously contributed to the country’s elasmobranch-reporting initiative. That initiative began in 2016 and was later formalized as “#pošaljiajkulu,” or “send the shark.” The shark was caught in a set gillnet deployed at 115 metres depth, approximately seven nautical miles offshore from the entrance to Boka Kotorska Bay.

Unlike the Croatian specimen, the Montenegrin shark was alive when the net was retrieved. The fisherman estimated its total length at approximately 1.3–1.4 metres. It was only lightly entangled, and it was released after photographs were taken. It appeared exhausted from its attempts to free itself and swam away slowly. The observation therefore documents a capture and release, not a tracked movement, measured survival outcome or demonstration that the animal remained in the area.

The records provide additional encounters beyond a previously published young-of-the-year great white shark caught near Rogoznica, Croatia, in September 2023. A widely used definition of a shark nursery requires newborn and young-of-the-year animals to be encountered more frequently than elsewhere, to remain in or return to the area for extended periods, and to use the habitat repeatedly across years. The two new records and the 2023 observation support repeated encounters, but they do not establish greater relative abundance, residency, return rates or long-term habitat use. The authors note that no unequivocal great white shark nursery has yet been identified in the Mediterranean basin.

Continental shelf habitat may nevertheless be relevant to the species’ early life stages. The Adriatic, Aegean Sea and Strait of Sicily contain extensive shelf areas shallower than 200 metres, with numerous islands in the Adriatic and Aegean. Telemetry studies conducted in other regions have found that young great white sharks generally occupy shallow coastal waters, often over insular shelves at sea-surface temperatures of 10–25°C, and other evidence indicates movement between the immediate shoreline and the middle continental shelf. These findings offer context for the Adriatic observations but do not show how either documented shark used the habitat.

The authors also discuss a possible relationship between Mediterranean warming and the distribution of young great white sharks, while emphasizing that the two records cannot test such a hypothesis. The Eastern Adriatic is warming, including at depth, and its broad shelf and coastal productivity could be relevant to early-stage sharks. However, a cluster of documented encounters could also reflect increased reporting and greater awareness among fishers rather than an ecological shift. The study’s small, opportunistic sample and reliance on fisher testimony prevent it from distinguishing a new ecological pattern from a previously overlooked aspect of the species’ early life history or determining whether the Eastern Adriatic is a stable nursery, a seasonal developmental and foraging habitat, or part of a broader network of Mediterranean habitats.

Subject of Research: Citizen-science records of young great white sharks in the Eastern Adriatic Sea

Article Title: Recent observations of two young-of-the-year great white sharks, Carcharodon carcharias ( Elasmobranchii , Lamniformes , Lamnidae ), in the Eastern Adriatic Sea

Article References: Ćetković, I., Bernardi, J., Ugarković, P., De Maddalena, A., Dragičević, B., Ikica, Z., & Pešić, A. (2026). Recent observations of two young-of-the-year great white sharks, Carcharodon carcharias (Elasmobranchii, Lamniformes, Lamnidae), in the Eastern Adriatic Sea. Acta Ichthyologica et Piscatoria, 56, 151-158. https://doi.org/10.3897/aiep.56.188503

Image Credits: AI Generated

DOI: 10.3897/aiep.56.188503

Keywords: great white shark, Eastern Adriatic, citizen science, shark bycatch, nursery habitat, Croatia, Montenegro, marine conservation, fisher observations, Recent, observations, young-of-the-year