Particle Tracking Used to Identify Spawning Sites of Western Baltic Herring

The identification of spawning sites of exploited fish stocks is particularly important for recruitment and conservation. Spawning-site fidelity has been discussed for many migratory fish species including Atlantic and Pacific herring, and might represent an important factor for the structuring of herring populations. However, identifying spawning sites in the field remains a challenge. In the present study we tried to examine specific hatching sites of Western Baltic Spring Spawning herring within its main spawning area, the Greifswalder Bodden, a shallow lagoon at the south of Rügen Island, Germany. We tracked herring larvae of 6–10 mm length, recorded by larval surveys during spawning seasons of 2003–2009, back to their hatching sites using a Lagrangian particle backtracking model. We compared areas identified by the model with results of earlier field studies and analysed variations between years, larval length groups, and different growth models. Results demonstrate large variations in the location of successful spawning sites, and that larvae up to 10 mm length were caught close to their origin. However, the precision of backtracking modelling is impeded by the wind induced diffusion in the area studied, which also causes larval retention as shown by a previous study.