Spreading the Risk: Native Trout Management in a Warmer and Less-Certain Future

Management strategies that increase biological diversity and promote varied approaches to population protection are more likely to succeed during a future in which global warming drives rapid environmental change and increases uncertainty of future conditions.We describe how the concept of a diversemanagement portfolio can be applied to native trout conservation by increasing representation (protecting and restoring diversity), resilience (having sufficiently large populations and intact habitats to facilitate recovery from rapid environmental change), and redundancy (saving a sufficient number of populations so that some can be lost without jeopardizing the species). Saving diversity for native trout requires the conservation of genetically pure populations, the protection and restoration of life history diversity, and the protection of populations across the historical range. Protecting larger stronghold populations is important because such populations will have a better chance of surviving future disturbances, including those associated with climate change. The long-term persistence of populations is likely to require management for larger population sizes and larger habitat patches than currently exist for many native trout populations. Redundancy among these elements is important given that many populations are small and occupy reduced habitat in fragmented stream systems and therefore are increasingly vulnerable to extirpation. Application of the concept is further described in case studies of Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri and Rio Grande cutthroat trout O. clarkii virginalis, two subspecies that illustrate many of the challenges that are common to management of western native trout.