In spite of the €1 billion of public money spent each year in Europe on monitoring and measuring the seas (COM/2010/0461), users are still confronted with restrictions on data access. When accessible, the quality of the data may be unknown or different standards and formats may apply which make data assembling from different sources a challenging and often specialists’ task. This situation seriously hampers the opportunities to develop innovative products and services, including the use of data in advanced scientific research. This is particularly true for long-term time-series. The current chapter covers the process of reconstructing time-series for different parameters that describe the sea fisheries in Belgium: landings, value of landings, species, species length classes, fishing areas, and their seasonal and annual variability. The process from source to product is explained and the main outcomes and data products of the reconstruction of historical time-series on Belgian sea fisheries are commented.