The marine resources in Senegal are still relatively abundant, and Senegalese fisheries generate a high economic value for local communities. These fisheries are characterized by a large number of distant-water fleets alternating between legal and illegal operations, depending on circumstances, and a rapid increase of artisanal fishing effort. The extent of the impact of artisanal fisheries on fisheries resources and the Senegalese economy is as poorly known as is the level of illegal unreported and unregulated (IUU) industrial fishing. The former relies on official surveys and voluntary reports by fishers, while the existence of the latter was largely denied in the past. Large and frequent ‘migrations’ (i.e., incursions into the waters of neighbouring countries) by Senegalese artisanal fishers, under-estimation of fishing effort and increasing conflicts over fisheries suggest that officially reported catch data do not reflect reality. A thorough literature review, experts and industry consultations were used to reconstruct Senegalese fisheries catch data. Official national data were compared to the data supplied to FAO and adjusted from 1950 to 2010. Reported and missing sub-sectors, including artisanal catches within and outside Senegalese waters, non-commercial sub-sectors, and industrial catches by the legal and illegal fleets, were conservatively re-assessed. The impacts of the intensive illegal fishing activities on artisanal fisheries and the economy were investigated. The results showed substantial under-reporting, ranging from 4 times higher than the official data in the past to about 1.6 times recently. Artisanal fisheries, according to official data, were responsible for 50% of total extractions, as opposed to 80% 20 years ago. However, while catches by migrant fishers increased dramatically, artisanal catches from Senegalese waters decreased despite an increasing effort, suggesting over-capacity. IUU catches, which were worth around $ 300 million US annually, whether transhipped or otherwise spirited out of Senegalese waters, or discarded, represent a huge loss to Senegal. Also, the foreign fleet, illegally exploiting Senegalese fisheries resources, impact strongly on the migrations of Senegalese artisanal fishers, who in turn increase their migrations as an adaptation strategy to meet their need for fish in the face of rapid resource depletion.