Any analysis of the impacts of fishing on marine systems, as undertaken by the Sea Around Us project (www.seaaroundus.org), imposes critical demands on fine spatial data documenting the extraction of marine resources. Data sources such as those provided voluntarily from fishing countries through the Food and Agriculture Organization (FAO) of the United Nations are invaluable but have many limitations. Regional datasets are also important in that they provide better detail. Reconstruction of national datasets can also provide great insights into historical catch series (e.g., Zeller et al., 2007), and are important to understand historic baselines (Jackson and Jacquet, this volume). These must be woven into one coherent and harmonized global dataset representing all extractions over time. To provide the necessary spatial detail, the global data are allocated to a fine grid of cells measuring just 30 by 30 minutes of latitude and longitude, resulting in over 180000 such cells covering the world's oceans. The taxonomic identity of the reported catch must be combined with comprehensive databases on where the species occur (and in what abundance) in order to complete this process. This spatial allocation must be further tempered by where countries fish, as not all coastal waters are available to all fleets. After considerable development by the Sea Around Us project, it is now possible to examine global catches and catch values in the necessary spatial context. Like detectives, we have been able to deduce who caught what, where, and when, and how much money they made in the process.