Essential spawning grounds of Scottish herring: current knowledge and future challenges

Scotland once had the largest herring fishery globally, generating local income, identity, and societal change. Following historic stock collapse, in spring 2018/2019 large herring shoals were observed on the west coast for the first time in decades, at a formerly important spawning ground. This highlights the urgency of maintaining historic (and contemporary) benthic spawning habitat, which these fish rely upon, in good condition. However, information on exact location, characteristics, and status of historic and contemporary spawning grounds, if existing, is not easily accessible. We searched over 1190 literature sources, dating back to 1884, using scientific databases and web-based searches, and ran a query for automated search of comprehensive historic reports. We present current knowledge on Scottish herring spawning grounds, retrieved through these searches and fisher interviews, maps showing historic and contemporary spawning grounds, and discuss challenges arising from the methods used to recognize these grounds. Knowledge gaps regarding location and environmental status of past and current spawning grounds, particularly relevant for Scotland’s west coast, are identified. Based on the importance of specific environmental and physical variables for herring reproductive success, we advocate the inclusion of essential spawning grounds into herring management plans. This will require additional data on spawning grounds, including historic local ecological knowledge rarely considered. An inclusive ecosystem-based approach to herring management would allow more targeted actions to conserve (and potentially restore) essential spawning habitat. More effective management strategies will also call for reversing the (global) issue of the disconnect between different stakeholder groups.