This article was featured in Eurofish Magazine 1 2026.
A recent study by the Thünen-Institute of Baltic Sea (dated 31 October 2025) shows that Atlantic herring in the Baltic Sea return to their birthplaces every year to reproduce. An international research team traced these movements by combining chemical “fingerprints” from otoliths—calcium carbonate structures that can be used to reveal the age and environmental history of the fish— with genetic analyses to identify individual fish origins and map reproductive migrations. The results indicate that 56 to 73 per cent of herring return to their birth area to spawn, regardless of the size of the spawning ground. This challenges the long-standing assumption that young, inexperienced fish simply join older shoals and learn migration routes to established spawning sites. Instead, the findings imply that different coastal spawning grounds are not interchangeable, which has direct implications for fisheries management and habitat conservation.
The work builds on earlier research into Baltic herring population dynamics, including a 1997 study that proposed migrating shoals incorporate “strays”, supporting genetic exchange among subpopulations and forming a wider metapopulation. By testing this hypothesis and estimating the proportions of returners and strays, the new study strengthens the case that local spawning habitats matter more than previously assumed. With coastal ecosystems facing increasing human pressures, the research highlights the value of targeted coastal zone management to safeguard spawning areas and support long-term stock productivity and marine ecosystem resilience.
