Study of the movement of Argyrosomus regius (Pisces, Teleostei) along the South-West coast of Portugal using network analysis

Background: The meagre (Argyrosomus regius) is a large coastal and semi-pelagic predator. Its distributions range from Norway to the Gulf of Guinea along the eastern Atlantic Ocean, the Mediterranean Sea, and the Black Sea. Due to its good-quality meat, its large size and the fact that it forms large spawning aggregations, it is frequently targeted by both recreational and commercial fisheries. Many studies called for a better assessment of its stocks and increased knowledge of its distributions, given its vulnerability to overfishing. Methods: Acoustic telemetry detections from 38 unique individuals were used. Network analysis techniques were applied to generate both spatial and social networks, allowing for the evaluation of meagre movements and aggregations along the Southwestern coast of the Iberian Peninsula. Results: Meagre migrations along the coast frequently involved precise locations, and many transitions occur between the South Coast and South-West Coast of Portugal, especially during the summer and autumn months. Although the observed aggregations were not significantly different from random, we have multiple detections of co-occurrences from two to six individuals. Most aggregations occurred along the South-West Coast of Portugal during summer-autumn months, suggesting that these locations represent valuable aggregation areas (potential feeding grounds) during meagre migrations. The tendency for long migrations was not homogeneously represented among individuals, with some fish displaying more frequent transitions throughout the Southwestern regions than others. Conclusions: Our findings provide valuable insights into the spatial ecology of meagre and align with previous research. These results can inform management and conservation efforts, particularly in the context of marine spatial planning.