Role of Connectivity in Survival and Persistence of Potamodromous and Non-Migratory Salmonids

Fish habitat is often implicitly perceived as a point in space, and substantial sums have been spent to determine the physical characteristics that define “good” habitat.  Concomitantly, however, most biologists recognize that fish move in relation to temporal fluctuations in habitat characteristics, such as discharge and temperature.  It is also apparent that habitat requirements change throughout the life-cycle of a fish, and habitat used for feeding, refuge, and reproduction may be spatially segregated, requiring movement to connect these different areas.  In fact, a dynamic life-history model provides a conceptual framework that is based on the idea that fish habitat can be represented by a network of points in space and time that is connected by movement.  It is apparent, therefore, that the ability to move among these habitat components is critical for the survival of individuals and persistence at higher levels of biological organization.  Physical, chemical, and biological factors that restrict movement (connectivity) among habitat components can have negative consequences for individuals, populations, and assemblages, within and among stream networks.  Here we use examples of potamodromous and non-migratory salmonids (coastal cutthroat trout, Colorado River cutthroat trout, Lahontan cutthroat trout, westslope cutthroat trout, Yellowstone cutthroat trout, bull trout, and Arctic grayling) to explore this conceptualization and discuss the importance of connectivity to the persistence of these charismatic fishes in the western USA.