Understanding behavioural rules in movements of marine megafauna

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Residency and space use estimation methods based on passive acoustic telemetry data

Publication . Kraft, Sebastian; Gandra, Miguel; Lennox, R. J.; Mourier, J.; Winkler, Alexander; Abecasis, David

Acoustic telemetry has helped overcome many of the challenges faced when studying the movement ecology of aquatic species, allowing to obtain unprecedented amounts of data. This has made it into one of the most widely used methods nowadays. Many ways to analyse acoustic telemetry data have been made available and deciding on how to analyse the data requires considering the type of research objectives, relevant properties of the data (e.g., resolution, study design, equipment), habits of the study species, researcher experience, among others. To ease this decision process, here we showcase (1) some of the methods used to estimate pseudo-positions and positions from raw acoustic telemetry data, (2) methods to estimate residency and (3) methods to estimate two-dimensional home and occurrence range using geometric or hull-based methods and density-distribution methods, a network-based approach, and three-dimensional methods. We provide examples of some of these were tested using a sample of real data. With this we intend to provide the necessary background for the selection of the method(s) that better fit specific research objectives when using acoustic telemetry.

2023-03-01Journal article

Open access

Movement patterns and connectivity of argyrosomus regius along the southwest coast of Portugal using network analysis

Publication . Fanna, Samuele; Gandra, Miguel; Kraft, Sebastian; Martínez Ramírez, Lucas; Vilas, Cesar; Winkler, Alexander; Abecasis, David

The meagre (Argyrosomus regius) is a large teleost inhabiting the coastal waters of the East Atlantic Ocean and the Mediterranean Sea. Along the Iberian Peninsula, it is frequently targeted by both commercial and recreational fisheries. Despite its relevance, information on its population structure and movement ecology has been scarce until recently. While these studies have provided a foundation, information on the main migratory corridors along the coast is still missing. The current study aimed to identify primary migratory routes, aggregations, and residency sites along the Southwest coast of Portugal. Forty-nine adult meagres were captured and tagged with acoustic transmitters between 2018 and 2023. Their movement was monitored from 122 acoustic receivers, grouped into 25 arrays, which were deployed throughout the Gulf of C´adiz and along the Southwest coast of Portugal. A spatial network approach was applied to analyse these data. The locations near the tagging site and along the Southwest coast displayed high values of eigenvector and betweenness centralities, indicating their crucial role in facilitating the connectivity of adult meagre between the two regions. Furthermore, co-occurrences outside the spawning season highlight their role as potential feeding grounds. The number of detections and co-occurrences near the Guadiana Estuary provides further evidence that the location may serve as a spawning ground, although additional data are needed to confirm this. Our findings expand previous research, identifying key passages and aggregation sites for meagre along the coast. These results can inform management and conservation efforts, particularly in the context of marine spatial planning.

2026-01Journal article

Restricted access