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

Abstract

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 diverse management 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.

Received May 16, 2011; accepted January 12, 2012

ACKNOWLEDGMENTS

We thank members of the Yellowstone Cutthroat Trout Interagency Workgroup for their discussion of climate change adaptation in western cutthroat trout. Our application of the portfolio theory to native trout has benefited from discussions with Warren Colyer, Dan Dauwalter, Kurt Fesenmyer, Bob Gresswell, Jeff Kershner, Joe McGurrin, Helen Neville, Kevin Reilly, Brad Shepard, and Bill Schudlich. We thank Robert Al-Chokhachy, Dan Dauwalter, Bruce Rieman, and three anonymous reviewers for their comments on earlier versions of the manuscript. Support for this research was provided by the USGS Global Change Research Program and Trout Unlimited's Coldwater Conservation Fund.