Conserving Peripheral Trout Populations: The Values and Risks of Life on the Edge

Abstract

AbstractPeripheral populations—generally defined as those at the geographic edge of the range—often have increased conservation value due to their potential to maximize within‐species biodiversity, retain important evolutionary legacies, and provide the fodder for future adaptation. However, there has been little exploration of their conservation value in aquatic systems. Inland cutthroat trout (Oncorhynchus clarkii) subspecies provide a unique opportunity to evaluate the distribution of peripheral populations and patterns of persistence across a wide range of environmental conditions. Our assessment analyzed range‐wide losses of peripheral and core populations since the 1800s, and evaluated the likelihood of persistence for remaining populations of five cutthroat trout subspecies: Bonneville, Colorado River, Yellowstone, Rio Grande, and westslope. For all five, we found that core and peripheral populations have declined substantially, but the amounts of habitat occupied by peripheral populations generally have declined at a greater magnitude. The more isolated peripheral populations typically exhibited the greatest declines. Remaining peripheral populations often failed to meet minimum persistence criteria. Our characterization of peripheral populations and their losses emphasizes the need for closer evaluation of conservation priorities and management actions for cutthroat trout and other Fish if the values of peripheral populations are to be maintained.