The Gordian knot: managing herring (Clupea harengus) bridging across populations, fishery units, management areas, and politics

The management of western Baltic spring spawning (WBSS) herring is challenged by the highly complex stock structure with a temporal and geographical distribution leading to conflicting interests among different stakeholder groups. The stock is exploited in the Baltic Sea (Subdivisions 22–24) and the North Sea (Division IIIa) by various EU—and in the latter case also non‐EU—fishing
fleets. For the two separate management areas, TACs are set at different times in the yearly TACsetting process by the EU and negotiating counties, which often result in conflicts over quota allocations among different management units. The WBSS herring stock spawns in the western Baltic Sea and migrates into the Kattegat and Skagerrak areas, where it mixes with North Sea autumn spawning (NSAS) herring. Recent development of otolith shape analysis has enabled a
high‐resolution separation of herring stocks in these waters, giving a more detailed picture of the actual stock mixing potentially undermining the current assumption of only three population components. We discuss how a higher resolution of spawning components may facilitate the estimation of local population‐related productivity, and how this in turn may be applied in an
advanced future management of several populations within one management unit