James Ketchum Mejia's Doctoral Research on Shark Ecology
James Ketchum Mejia

Current UC MEXUS-CONACYT Doctoral Fellow, James Ketchum Mejia, has contributed his expertise on shark migration to the National Geographic Channel's Explorer television program on the "shark superhighway," a corridor in the tropical eastern Pacific through which hammerhead sharks migrate from island to island. Ketchum Mejia is currently in his 5th year of doctoral studies in the Graduate Group of Ecology at UC Davis under the guidance of Dr. A. Peter Klimley, director of UC Davis Biotelemetry Laboratory. For the past nine years, Ketchum Mejia has studied sharks, exploring shark ecology in the Gulf of California and shark movement patterns in Malpelo Island in Colombia and the Galapagos Islands in Ecuador.

Shark populations are in decline worldwide, and yet sharks play a critical ecological role in marine ecosystems. Ketchum Mejia's doctoral research may identify new alternatives to conserving and managing marine resources. Focusing on the Galapagos Marine Reserve, one of the largest marine-protected areas in the world, he is analyzing the fine- and large-scale movements of hammerhead, Galapagos, and whale sharks-species that have not been studied systematically in this region nor included under the original design of the reserve. Through the use of ultrasonic and satellite tags to track sharks' movements and dive patterns, sonar and oceanographic instruments to record the physical features of the ocean, and satellite imagery of sea surface temperature and chlorophyll, he hopes to determine the physical characteristics of sharks' habitat, including "hotspots" or regions where sharks are in abundance.

Thus far, Ketchum Mejia and the scientific team have tagged over one hundred hammerhead, five Galapagos, and four whale sharks in the Galapagos Islands. Preliminary results from this work have helped him to identify shark hotspots at Darwin and Wolf Islands in the northern part of the archipelago, where the diversity of marine predators peaks in association to specific conditions (e.g. topography, strong currents). These results also point to a high degree of shark movement between such islands in the Galapagos, leading to the discovery of a true shark superhighway. Ketchum Mejia is also testing a new technique for the design of marine reserves, the Seascape Species Approach (SSA), which builds upon the Landscape Species Approach used in terrestrial environments. He is hopeful that his work will provide answers to where, why, and how sharks move and develop an alternative method for marine conservation with application to other regions and environments. In the future, he would like to continue his research in the Gulf of California and the Mexican Pacific. He is particularly interested in the Revillagigedo Archipelago, a group of islands in Mexico with a large presence of marine predators at risk of disappearing due to illegal fisheries and lack of conservation management and enforcement.

James Ketchum Mejia is a member of the Biotelemetry Laboratory at UC Davis headed by Dr. A. Peter Klimley. His doctoral research is part of a larger collaborative project between UC Davis, the Charles Darwin Foundation, and the Galapagos National Park. For additional information, Ketchum Mejia can be contacted at jtketchum@ucdavis.edu. Ketchum Mejia can be seen in the "Shark Superhighway" episode here.