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Developing a Diverse Conservation Portfolio for Bonneville Cutthroat Trout

Amy Haak, Jack Williams, and Warren Colyer

Overview

Ensuring the long term persistence of native cutthroat trout in an era of rapid environmental change due to global warming, spread of invasive species, and other factors, requires a diverse conservation portfolio that spreads the risk of loss in an uncertain future across a variety of habitats, populations and management approaches. Rangewide diversity for native trout includes genetic integrity, life history diversity, and geographic (or ecological) diversity. A management portfolio that includes multiple examples of these elements of diversity and large patches of interconnected habitat for resiliency provides a ‘no regrets approach’ for reducing the threat of biodiversity loss due to climate change. The 3-R framework (Schafer and Stern 2000) provides a structure for describing existing levels of diversity for a subspecies:

  • Representation – saving existing elements of diversity;
  • Resiliency - having sufficiently large populations and intact habitats to facilitate recovery from large disturbances and rapid environmental change;
  • Redundancy – saving enough different populations so that some can be lost without jeopardizing the subspecies.

For a detailed explanation of the Conservation Portfolio concept, please view the paper Spreading the Risk: Native Trout Management in a Warmer and Less Certain Future (pdf).

Portfolio Map

The status of the existing portfolio for Bonneville cutthroat trout is summarized at the population level for each of the four occupied river basins within the historical range. The lack of resilience and low redundancy in the West Desert and Southern Bonneville basins underscores the vulnerability of these small, mostly isolated populations to environmental change. Although the Northern Bonneville and Bear River basins contain all of the portfolio elements, further work is needed to secure them. The relatively low population counts for genetic integrity are indicative of the threat posed by hybridization while the low counts for redundancy indicate that many of the genetically pure populations do not meet the minimum criteria for persistence. The Bear Lake population supports the largest genetically unaltered population remaining (218 km) while the Chalk Creek population in the Northern Bonneville has the second largest extent (179 km). Controlling nonnative species and restoring large interconnected populations throughout the historical range will increase the resilience of the entire portfolio.

      Representation Resiliency Redundancy
Basin Total Number of Pops. Occupied Stream Habitat (km) Genetic Integrity (pops.) Life Hist. Diversity (pops.) Geographic Diversity (pops.) Stronghold (pops.) Metapop (pops.) Persistent or Replicate and <=10% introgressed
Bear River 37 1727 19 5 adfl.
8 fluv.
2 both
NA 10 4 15
  • Restore and secure life history diversity and resiliency through watershed-scale projects such as the Bear River Watershed Restoration effort that is reconnecting populations while controlling nonnative trout.
  • Secure life history diversity and resilience by protecting and restoring important habitats.
Northern Bonneville 73 1344 43 3 adfl.
6 fluv.
NA 10 2 26
  • Restore metapopulation by reconnecting habitat in the upper Weber River system.
  • Restore life history diversity and build resilience in upper Jordan River by controlling nonnative trout and reconnecting populations.
Southern Bonneville 25 150 24 0 10 disj. 0 0 5
  • Increase redundancy and secure genetic integrity and geographic diversity by extending populations where possible and otherwise replicating populations into suitable habitats.
West Desert 29 127 28 0 29 disj. 0 0 8
  • Increase redundancy and secure genetic integrity and geographic diversity by extending populations where possible and otherwise replicating populations into suitable habitats.
Total 164 3348 114 24 39 20 6 54

Table 1. Results of the 3-R Framework for Bonneville cutthroat trout by river basin.

For more summary results, please see the Conservation Portfolio for Bonneville Cutthroat Trout (pdf)

For detailed, subbasin-level results, please see the full report, Developing a Diverse Conservation Portfolio for Bonneville Cutthroat Trout (pdf)