People have been observing and recording information on the marine environment for hundreds of years. Historians - and fishers - thus have unique access to valuable knowledge directly applicable to conservation and sustainable management. Yet they - and the spheres of knowledge they command - remain underused by rigid modern quantitative scientific approaches, where 'long-term' data can mean just a few decades, risking 'shifting baseline syndrome'. Drawing on unconventional knowledge is therefore essential for the effective current and future management of our natural environments, especially in the context of policy aiming to restore ecosystems, and in a changing climate. Our research will ask: can historians and scientists effectively convert historical information into knowledge that directly and tangibly informs marine ecosystem management for today and tomorrow? We will demonstrate the synergistic value of bringing together these disciplines to unlock the potential of historical data on a marine ecosystem component of fundamental importance in the northeast Atlantic, herring Clupea harengus. The herring had vast fisheries around the UK until their collapse around the mid-20th century. Modern scientific surveys identifying the spawning grounds of herring - sensitive to human pressures and in need of protection - after this, in the 1970s. They may therefore overlook historically important spawning grounds, which can suddenly be recolonised by recovering stocks. Using historical sources from the 17th to early 20th centuries - such as writings of early modern naturalists and travellers, newspaper archives, and Government enquiries, and the memory of living fishers - we will identify ecologically important herring spawning areas and characterise the long-term century-scale variation in spawning activity in response to changing climate, while advancing our knowledge of the social, economic and cultural context in which this knowledge was recorded. Identifying these areas using a cross-disciplinary integration of knowledge therefore has the potential to contribute to the sustainable management of herring, and the economic activity (fisheries) and other species (top predators, e.g. seabirds, sharks) which depend on it.