Ecology is the study of populations or communities.
Fisheries management is the manipulation of populations or environments to permit a sustainable harvest or to prevent extinction. Management is basically applied ecology. Unfortunately in many, perhaps most, cases the underlying ecology is inadequately known, forcing the manager to make dangerous inferences from inadequate data. As a consequence, many management decisions are tentative and often made in such a way as to generate data on which to base more realistic future decisions. Unfortunately the political consequences of this can be devastating.