Callinectes sapidus is an invasive species in the Mediterranean Sea, causing significant impacts on native biodiversity and small-scale fisheries. In Sardinia, the species was first recorded in 2017 and has rapidly spread to several coastal lagoons. To study its expansion and support management actions, the Autonomous Region of Sardinia promoted a scientific monitoring program aimed at assessing its distribution, abundance, and population dynamics in 14 lagoons under regional concession. The monitoring programme was carried out through a coordinated effort between the University of Cagliari and Sassari. Here, we report data from monthly samplings conducted over a 19-month period in seven lagoons monitored by the University of Cagliari: two on the west coast (S'Ena Arrubia, Cabras), two on the south (Santa Gilla, Porto Pino) ​​and three on the east (Colostrai, Feraxi and San Giovanni). Specimens were collected using baited pots equipped with four entrances and double chamber. The sampling design was based on a Triple-Catch-Unit (TCU), consisting of three traps arranged in a triangular configuration. The number of TCUs varied on the lagoon surface area. Traps were left fishing for 24 h to standardize catch per unit effort (CPUE).

The study assessed CPUE, population structure and reproductive dynamics across spatial and temporal scales. Among the investigated lagoons, Colostrai showed the highest CPUE, whereas no individuals were recorded in Cabras throughout the monitoring period. Our results highlight the presence of a stable population, with a marked presence of ovigerous females occurring from April to October, indicating an extended reproductive period. Juveniles were mainly observed from March to July in stations located farther from lagoon sea inlets. The sex ratio favored males, except in Santa Gilla.

These findings provide useful information for the development of science–based management strategies of the species, aimed at reducing the ecological and economic impacts of C. sapidus.