Fish Physiology, Volume 40B recently celebrated its 50th Anniversary. The editors of the series have produced a total of 47 books (several volumes have two books) that contain almost 500 chapters since the inaugural volume published in 1969. Initial volumes were devoted to understanding the basic mechanisms and principles of fish physiology, with a focus on a few model species and some application to natural environmental conditions. Then, as the field better understood mechanisms, the approach was broadened to not only delve deeper into system physiology (e.g., chapters in early volumes were expanded to become books), but also interspecific differences in physiology.Finally, as interspecific physiological mechanisms were further resolved, it became possible to discuss physiology in light of a changing world. Thus, physiology can now inform on conservation, sustainability and management, as exemplified with the most recent volumes. This anniversary issue celebrates the series by highlighting some of the very important early work in the field that was published in the series. - Contains reviews written by experts in the field of some of the early influential chapters from the series "Fish Physiology" - Highlights how some of this early work in the series "Fish Physiology" has stood the test of time and shaped the field today - Reintroduces some of the early influential work in the series "Fish Physiology" to new researchers in the field