The conservation benefits of the Galapagos Marine Reserve (GMR), created in March 1998, have been consistently proved for endemic species and populations with limited movements. Yet, to date, no study has explored its effects on highly-migratory pelagic species, such as tuna. To this end, the impact of the GMR on the behavior and productivity of tuna fisheries in this region is analyzed. After considering other potential factors, which occurred approximately over the same period (i.e. increase of fleet size, changes in fishing technology, and climatic events, among others), it was found that the creation of the GMR increased fishing productivity in both the Galapagos Exclusive Economic Zone (EEZ) surrounding the GMR, as well as inside the marine reserve. However, the effect was heterogenous among tuna species – the GMR had a positive impact on the fishing productivity of yellowfin tuna (YFT) and skipjack tuna (SKJ) fisheries, but did not have any significant effect on that of bigeye tuna (BET). Then, it is proposed that the GMR effect might be dissipated by the overuse of Fish Aggregating Devices (FADs), especially in the case of BET.