As a Conservation Biologist with The Bay Institute, Jon Rosenfield represents institute in various planning efforts to protect and restore the San Francisco Estuary and its watershed, including its numerous endangered species. He began collaborating with institute in the early 1990s when he worked as a Research Associate for the (then) Sierra Club Legal Defense Fund (now Earthjustice Legal Defense Fund) on litigation to protect the San Francisco Estuary's delta smelt and Sacramento River winter-run Chinook salmon.

He has degrees from Cornell University, the University of Michigan, and the University of New Mexico. Jon has served as the Director of Scientific Peer-review for the CALFED Ecosystem Restoration Program, California Coordinator for the Save our Wild Salmon coalition, and as Board President and Treasurer for the SalmonAID Foundation.