This book arises as a result of the formation of an International Network on Continental Fisheries Resources sponsored by the Secretaría de Políticas Universitarias (Secretary of University Policies). The authors are professors from Universities of Argentina, Chile, Uruguay and Brazil, a fact that constitutes an unprecedented experience for Ichthyology. The work brings together different topics of the species of "pejerreyes" that inhabit South America, with greater reference to Odontesthes bonariensis, the "king fish" of the Argentines. It is aimed to researchers, teachers, students, managers, fishermen, officials, agricultural producers and other actors in the fishing sector, as well as the public in general interested in deepening their knowledge about the "pejerrey" resource.