Bull trout (Salvelinus confluentus) COSEWIC assessment and status report 2012

Official title: COSEWIC Assessment and Status Report on the Bull Trout Salvelinus confluentus in Canada - 2012

• Next page

• South Coast British Columbia populations
• Western Arctic populations
• Upper Yukon Watershed populations
• Saskatchewan - Nelson Rivers populations
• Pacific populations

South Coast British Columbia populations - Special Concern
Western Arctic populations - Special Concern
Upper Yukon Watershed populations - Data Deficient
Saskatchewan - Nelson Rivers populations - Threatened
Pacific populations - Not At Risk
2012

Table of Contents

Document Information

• COSEWIC Assessment Summary
• COSEWIC Executive Summary
• Technical Summary: DU1- Southcoast British Columbia populations
• Technical Summary: DU2 - Western Arctic populations
• Technical Summary: DU3 - Upper Yukon Watershed populations
• Technical Summary: DU4 - Saskatchewan-Nelson Rivers populations
• Technical Summary: DU5 – Pacific populations
• Wildlife Species Description and Significance
  • Name and Classification
  • Morphological Description
  • Population Spatial Structure and Variability
  • Designatable Units
  • Special Significance
• Distribution
  • Global Range
  • Canadian Range
• Habitat
  • Habitat Requirements
  • Habitat Trends
• Biology
  • Life History Diversity
  • Reproduction
  • Diet
  • Physiology and Adaptability
  • Dispersal and Migration
  • Anadromy
  • Interspecific Interactions
  • Interspecific Competition with Native Salmonines
  • Interspecific Competition with Non-native Salmonines
• Population Sizes and Trends
  • Sampling Effort and Methods
  • Abundance
  • Effective Population Size
  • Fluctuations and Trends
  • Rescue Effect
• Threats and Limiting Factors
  • Naturally Occurring Limiting Factors
  • Anthropogenic Threats
  • Loss of Habitat Network
  • Interaction with Introduced Species
  • Overexploitation
• Protection, Status, and Ranks
  • Legal Protection and Status
  • Non-Legal Status and Ranks
  • Habitat Protection and Ownership
• Acknowledgements and Authorities Contacted
• Information Sources
• Biographical Summary of Report Writer(s)
• Collections Examined

List of Figures

• Figure 1. Bull Trout (Salvelinus confluentus). Picture courtesy of J.D. McPhail and D.L. McPhail.
• Figure 2. Distribution of two major Bull Trout mitochondrial DNA lineages identified by restriction fragment length polymorphism of 47 Bull Trout populations (N = 348). The solid black line dividing groups A (Genetic Lineage 1) and B (Genetic Lineage 2) is the approximate location of the Cascade/Coast Mountain crest. Sourced from Taylor et al. 1999.
• Figure 3. UPGMA dendogram of pairwise sequence divergence estimates from 21 restriction fragment length polymorphism mitochondrial DNA haplotypes. Includes 348 Bull Trout samples analyzed from 47 populations. For each haplotype, geographical locations in which it occurred are listed. Sourced from Taylor et al. 1999. Genetic lineages and probable anadromous populations (*) indicated.
• Figure 4. UPGMA dendogram of genetic similarity among 373 samples of Bull Trout from 20 populations estimated from variation across 7 microsatellite loci. Numbers along branches represent bootstrap scores from 1000 pseudoreplicate analyses. Sourced from Taylor and Costello 2006. Genetic lineages and probable anadromous populations (*) indicated.
• Figure 5. Canadian distribution of Bull Trout. Data from: Province of British Columbia (2007); Rodtka 2009; Laframboise (pers. comm. 2010); Parkinson (pers. comm. 2010); Mochnacz et al. (submitted); Reist and Sawatzky (in prep.); Hagen and Decker (2011).
• Figure 6. Approximate current and historical global range of Bull Trout. Distribution is not continuous throughout range. Historical range sourced from McPhail and Baxter 1996; current range modified from Figure 5, USFWS2008, Rodtka 2009).
• Figure 7. Generic habitat use by Bull Trout throughout their life cycle. Modified from Stewart et al. 2007a.
• Figure 8. Generalized food web for Bull Trout showing the direction of energy flow. Bold lines indicate major food pathways, in comparison to thinner lines; solid lines indicate demonstrated and dashed lines putative pathways. Sourced from Stewart et al. 2007b.
• Figure 9. The parapatric species distributions of Dolly Varden (stipled), Bull Trout (shaded), and their overlap (stipled-shaded) in western Canada. Sourced from Baxter et al. (1997). Thutade Lake area studied in that manuscript is highlighted.
• Figure 10. Distribution of northern Bull Trout and Dolly Varden, showing new records from Mochnacz et al. (submitted) and point distributions from known and uncertain literature records. General distributions follow drainage basins and known point distributions. Only partial drainages are shown. Sourced from Mochnacz et al. (submitted).
• Figure 11. Spatial distributions of Bull Trout core areas in Alberta and their conservation ranking. Assessment was performed by the Fish and Wildlife Division of Alberta Sustainable Resource Development and is based upon a modification of the Natural Heritage Network ranking methodology using NatureServe Conservation Status Assessment Criteria. Extirpated core areas are not shown. Figure prepared by Velma Hudson (Alberta Conservation Association) and sourced from Rodtka (2009).

List of Tables

• Table 1. Summary of 31 adult Bull Trout abundance datasets compiled from 22 core areas from 12 of 26 Bull Trout Ecological Drainage Units (EDUs) identified in British Columbia. Trend data (simple regression analysis) available for 23 of these datasets covering 11 Bull Trout EDUs (datasets with more than five years of data collected using a consistent methodology). Modified from Hagen and Decker (2011).
• Table 2. Summary of threats assessment for Bull Trout within each designated unit (DU). Threats recorded according to the IUCN classification system. Impacts calculated from recorded scope and severity values (‘Not Calc.’ refers to values not calculated because they lay outside of the assessment timeframe). Assigned overall threat impact may vary from the calculated value based on best professional judgment.
• Table 3. Authorities contacted during the preparation of this report.

List of Appendices

• Appendix 1.  Conservation rank, estimated adult population abundance, stream occupancy (km), short-term trend, and the severity, scope and immediacy of threats to the 51 identified Bull Trout core areas in Alberta. Assessment was performed by the Fish and Wildlife Division of Alberta Sustainable Resource Development and is based upon a modification of the Natural Heritage Network ranking methodology using NatureServe Conservation Status Assessment Criteria (estimated adult population abundances (using quantitative data and/or expert opinion) are accompanied by appropriate NatureServe Range Categories in parenthesis, and were subject to a core areas status exercise based on methodology of Fredenberg et al. (2005). The focus of the review was on core areas currently occupied by Bull Trout, and therefore this is not a comprehensive list of extirpated core areas. Modified from Rodtka (2009) and Girard (pers. comm. 2010).
• Appendix 2.  Conservation rank, estimated adult population abundance, stream occupancy (km), short-term trend, and threats to the 115 identified Bull Trout core areas in British Columbia. Assessment was performed by the British Columbia Ministry of Environment and is based upon a modification of core areas assessment methodology of Fredenberg et al. (2005) using quantitative data where available (see * below) and expert opinion. The severity, scope, and immediacy of threats identified is listed for each core area. Conservation status rank given for each core area, as well as overall for each of the 26 identified Bull Trout Ecological Drainage Units (EDUs) using the weighted average of assigned status ranks for each EDU’s core areas. * Indicates one of 31 available adult Bull Trout abundance datasets (number in parenthesis when more than one dataset for a core area). See Table 1 for more details. Modified from Hagen and Decker (2011).
• Appendix 3.  Land-use events and Bull Trout declines in the Oldman River Basin, southwestern Alberta. Sourced from Rodtka (2009).