Sepulveda is a fisherman and a research scientist. He has focused primarily on pelagic fish ecology and fisheries biology. Sepulveda attended California State University, Fullerton for his Bachelors and Masters degrees and later attended Scripps Institution of Oceanography for his doctoral work. At Scripps, Sepulveda worked with the late Dr. Jeffrey Graham on studies related to the movements and physiology of regionally-important species like the common thresher and mako sharks. Sepulveda transitioned to the Pfleger Institute in 2005 where he is now the director of research and education. At PIER Sepulveda has re-directed the Institute’s focus towards applied field research on species of regional importance. Specifically, Sepulveda's research interests are focused on addressing questions related to the sustainable management of California’s marine resources. Lastly, Sepulveda is an advocate of sustainable fishing operations, both recreational and commercial and enjoys the ocean on many levels.