This text provides a synthesis of quantitative information on the ecology of the brown trout, including sea-trout, and comparisons with closely related species such as the Atlantic salmon, Pacific salmon, and rainbow trout. Much of this work, especially the case studies, is relevant to general problems in quantitative animal ecology as well as to fisheries management. One theme emphasized throughout is the development, testing, and use of realistic mathematical models as important tools for conservation and management of fish and other animals. Ecologists (postgraduate students and professionals), fish biologists, fisheries managers, should find this work of interest.