Ramon Margalef López (1919-2004) was one of the most prominent scientists of the 20th century in the fields of limnology, oceanography and ecology. His contributions to theoretical ecology, which won him international recognition, were based on a great deal of laboratory and field work and on extensive observations of the natural world, a passion that he acquired at a young age. Some of the early papers of Ramon Margalef appeared in the Publicaciones del Instituto de Biología Aplicada, but as of 1955 many of his marine studies were published in Investigación Pesquera, the journal of the Instituto de Investigaciones Pesqueras of the CSIC in Barcelona. He also wrote several articles for Scientia Marina, the journal that replaced Investigación Pesquera in 1989 after the Instituto de Investigaciones Pesqueras became the Institut de Ciències del Mar. The present article aims to give an overview of Margalef’s contributions to these journals to mark the celebration in 2019 of the 100th anniversary of his birth.