In the fourth episode, I interviewed Dr. James T. Carlton, Professor Emeritus of Marine Sciences at Williams College, Director Emeritus of the Williams College-Mystic Seaport Maritime Studies Program, Fellow of the American Association for the Advancement of Science, founding Editor–in–Chief of Biological Invasions, and a distinguished Pew Fellow in Marine Conservation. Since 1962, Dr. Carlton has been a pioneering force in marine ecology and biological invasions research. His nine congressional testimonies have directly shaped national invasive species legislation.