James Deacon was born at home in White, South Dakota. For the first few years of his life, the family moved around a lot to accommodate his father's job as school superintendent. Their summers were spent in a cabin on a lake, where Jim helped his grandparents in their store, seining minnows, clerking, and storing ice. From his eighth grade year through high school graduation, the family lived in Aberdeen, South Dakota.
Jim attended college on a tuition scholarship in Wichita Falls, Texas. He majored in biology and education, and then went to grad school at the University of Kansas. His favorite undergraduate professor knew the fish expert there and encouraged Jim to study fish.
He graduated in the summer of 1960, and started applying for jobs. He interviewed with Dean Bill Carlson for a job at UNLV, which was then called University of Nevada Southern Regional Division. In 1964, Jim and his family moved to Reno and he taught two summers at UNR.
As professor of biology, Jim focused on getting students involved in field studies as well as classroom work. He was instrumental in organizing the Department of Environmental Studies, which started in 1992. He also helped develop a master's program and a Ph.D. program in biology. He is best known for his expertise and involvement in the study of the Devil's Hole pup fish, an endangered Nevada species of fish.