Mixed-stock analysis of Atlantic herring (<i>Clupea harengus</i>): a tool for identifying management units and complex migration dynamics
Dorte Bekkevold, Florian Berg, Patrick Polte, Valerio Bartolino, Henn Ojaveer, Henrik Mosegaard, Edward D. Farrell, Jelena Fedotova, Jakob Hemmer‐Hansen, Bastian Huwer, Vanessa Trijoulet, Christoffer Moesgaard Albertsen, Angela P. Fuentes‐Pardo, Tomas Gröhsler, Mats E. Pettersson, Teunis Jansen, Arild Folkvord, Leif Andersson
Abstract
Abstract We developed and validated a mixed-stock analysis (MSA) method with 59 single-nucleotide polymorphisms selected from genome-wide data to assign individuals to populations in mixed-stock samples of Atlantic herring from the North and Baltic seas. We analysed 3734 herring from spawning locations and scientific catches of mixed feeding stocks to demonstrate a “one-fits-all” tool with unprecedented accuracy for monitoring spatio-temporal dynamics throughout a large geographical range with complex stock mixing. We re-analysed time-series data (2002–2021) and compared inferences about stock composition with estimates from morphological data. We show that contributions from the western Baltic spring-spawning stock complex, which is under management concern, have likely been overestimated. We also show that a genetically distinctive population of western Baltic autumn spawners, ascribed low fisheries importance, contributes non-negligible and potentially temporally increasing proportions to mixed-stock aggregations, calling for a re-evaluation of stock definitions. MSA data can be implemented in stock assessment and in a variety of applications, including marine ecosystem description, impact assessment of specific fleets, and stock-rebuilding plans.