LIFE-HISTORY ORGANIZATION OF YELLOWSTONE CUTTHROAT TROUT (ONCORHYNCHUS-CLARKI-BOUVIERI) IN YELLOWSTONE LAKE

Life-history organization of the cutthroat trout (Oncorhynchus clarki) may be viewed at Various levels, including species, subspecies, metap opulation, population, or individual. Each level varies in spatial sca le and temporal persistence, and components at each level continually change with changes in environment. Cutthroat trout are widely distrib uted throughout the western United States, occurring in such diverse e nvironments as coastal rivers of the Pacific Northwest and interior st reams of the Great Basin. During its evolution the species has organiz ed into 14 subspecies with many different life-history characteristics and habitat requirements. Within subspecies, organization is equally complex. For example, life-history traits, such as average size and ag e, migration strategy, and migration timing, vary among individual spa wning populations of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) in tributary streams of Yellowstone Lake. Understanding the effects of human perturbations on life-history organization is critica l for management of the cutthroat trout and other polytypic salmonid s pecies. Loss of diversity at any hierarchical level jeopardizes the lo ng-term ability of the species to adapt to changing environments, and it may also lead to increased fluctuations in abundance and yield and increase the risk of extinction.