IMIS

The blue crab (Callinectes sapidus) is a non-indigenous species originating from the Atlantic Ocean that has colonized the Mediterranean Sea. Since it 's first record in Slovenia in 2019, it 's abundance and distribution have increased. It 's tolerance of varying salinities and habitats facilitates establishment in coastal environments. Males are more commonly associated with lower-salinity habitats, whereas females prefer more saline waters. Mating occurs in estuarine and transitional habitats, after which females move to more saline waters to release larvae. This study aimed to investigate blue crab occurrence in Landscape Park Strunjan, including Stjuža Lagoon, the salt pans, Roja Stream, and the marine environment, and determine movements between them. Between June and August 2026, 33 individuals were tagged for acoustic and radio telemetry: 8 in the marine environment (four females, including two ovigerous females, and four males) and 25 males in Stjuža Lagoon. All received acoustic transmitters, while 10 lagoon males were additionally equipped with radio transmitters. Acoustic telemetry relied on three stationary marine receivers, whereas radio telemetry involved manual tracking in the lagoon and salt pans. Acoustic telemetry detected 9 individuals: six marine and three lagoon. Two lagoon males were monitored using both methods, providing complementary data that helped identify movement routes between habitats. Missing detections may indicate movement beyond the monitoring area or transmitter battery depletion. Overall, the results demonstrate that combining acoustic and radio telemetry is suitable for monitoring blue crab movements across interconnected habitats. Future studies should improve receiver coverage, use longer-lasting transmitters, and extend radio tracking for precise movement data.