We present a compilation of published telemetric results, complemented by the addition of new results where necessary, to justify the expansion of the marine protected areas in the Eastern Pacific. In addition, we furnish evidence that fishing effort by commercial vessels, carrying position-monitoring, satellite-communicating radio beacons, has diminished within their boundaries. Researchers have described the movement ecology of nine species of sharks at these insular sites: the Galapagos archipelago off Ecuador, Malpelo Island off Colombia, Cocos Island off Costa Rica, and the Revillagigedo archipelago off Mexico. Mainly two telemetric techniques have been utilized: (1) placing coded ultrasonic beacons on individuals and detecting their presence with autonomous receivers deployed along the coasts of the islands and (2) outfitting individuals with SPOT and PSAT tags: the former enabling the ARGOS satellite to detect surface-swimming individuals, the latter releasing from individuals and rising to the surface to transmit geolocation based-positions to the same satellite. This information has enabled Mexico to create the Revillagigedo National Park, Colombia to increase the size of the Malpelo Fauna and Flora Sanctuary, and Costa Rica to create a protective corridor between Cocos and the Las Gemelas seamounts. Satellite tracking of sharks outside the current boundaries of the Galapagos Marine Reserve supports the need to increase its size in the future. Hence, telemetric studies have played and continue to serve an essential role in providing a well-supported rationale for research managers to match the size of their marine reserves to the spatial ecologies of the species within them.