BC Conservation Data Centre: Conservation Status Report
Salvelinus confluentus pop. 28
Bull Trout - South Coast Population
| Scientific Name: | Salvelinus confluentus pop. 28 |
|---|---|
| Scientific Name Synonyms: |
Salvelinus confluentus pop. 6
|
| English Name: | Bull Trout - South Coast Population |
| Provincial Status Summary | |
| Status: | S2S3 |
| Date Status Assigned: | April 26, 2018 |
| Date Last Reviewed: | April 26, 2018 |
| Reasons: | This species is highly sensitive to increasing temperatures as it is cold-dependent. While declines have been observed in some watersheds, others have witnessed recent increases associated with more restrictive angling regulations. Populations considered to be at low-risk to potentially at-risk depending on the watershed. Overall, populations are probably stable at present but significant uncertainty and threats persist associated with climate change, altered flow regimes and other identified threats in this highly developed region of BC. |
| Range | |
| Range Extent: | F = 20,000-200,000 square km |
| Range Extent Estimate (km2): | 32053 |
| Range Extent Comments: | COSEWIC (2012) states that the total South Coast British Columbia DU is found in 32,053 square km. |
| Area of Occupancy (km2): | G = 501-2,500 |
| Linear Distance of Occupancy: | U = Unknown |
| Area of Occupancy Comments: | COSEWIC (2012) lists the total South Coast British Columbia DU as being in greater than 2000 square km of 2x2 grid value. |
| Occurrences & Population | |
| Number of Occurrences: | B = 6 - 20 |
| Comments: | COSEWIC (2012) lists the number of BC populations is apporximately 5-10. |
| Number of Occurrences with Good Viability / Ecological Integrity: | AB = 0 - 3 |
| Comments: | The Squamish populations is at risk in this DU (COSEWIC 2012). The Skagit population was originally classified as at low risk in COSEWIC (2012); however, there have been recent reports of Eastern Brook Trout in the system. |
| Number of Occurrences Appropriately Protected & Managed: | Rank Factor not assessed |
| Comments: | The number of protected occurrences is unknown. Bull trout habitat is protected by the federal Fisheries Act. |
| Population Size: | DE = 1,000 - 10,000 individuals |
| Comments: | Bull trout estimates for the South Coast British Columbia DU include 1750 mature individuals for Skagit, and approximately 575 mature individuals for Squamish, for a total of over 2325 fish (range of known populations: 1250-3500; COSEWIC 2012). |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | B = High |
| Comments: |
From 2017-12-19 TC: Generation time is approximately 7 years, therefore 21 years was the timeframes used for scoring severity and timing (COSEWIC 2012). There is not a lot of population and trend information available for the many different bull trout populations and designatable units found throughout BC (COSEWIC 2012; Hagen and Decker 2011). Many of the populations studied show stable or increasing trends, however certain regions, such as the heavily developed Lower Fraser, show overall declines (Hagen and Decker 2011). There has been no evidence of decline in numner of mature individuals (COSEWIC 2012). This DU is located entirely within BC, in 5 watersheds: Lillooet, Lower Fraser, Lower Fraser Canyon, Skagit and Squamish. The majority (1750 out of more than 2325 individuals) of this DU is found in the Skagit system, with approximately 575 individuals found in the Squamish system and lower numbers in the other 3 locations. The main threats are from habitat degradation and fragmentation from forestry and the associated road building; introduced brook trout, which can displace and/or hybridize with native bull trout; overexploitation (through illegal harvest and incidental by-catch, as well as intense angling efforts; however, there are adaptive management plans and angling regulations in place in many regions as well); and increasing temperatures, due to climate change or change in forest cover (COSEWIC 2012; Hagen and Decker 2011). The anadromous life history form is unique to these populations. Bull trout are voracious piscivores, and can be very vulnerable to angling effort (Hammond 2004). Bull trout are very sensitive to forestry impacts, as the loss of riparian vegetation and subsequent loss of shading can lead to temperature increases in the streams (McPhail and Baxter 1996; Hammond 2004). Forestry impacts can also lead to an increase of sedimentation, which affects the incubation and rearing habitat (Hammond 2004). Any increase of temperature due to climate change will also have negative impacts on this cold-water adapted species (McPhail 2007). Overall threat impact was assessed as medium-high given uncertainties of climate change for this temperature sensitive species, and fairly limited range all of which occurs in a highly developed region with ongoing developmental pressures. |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | FH = Decline of <30% to increase of 25% |
| Comments: | There is no information for three of the river systems, the Lillooet, lower Fraser and Lower Fraser Canyon; the Skagit was listed as low risk and an increasing population, and the Squamish was listed as at risk with declines by COSEWIC (2012). Thus the trend varies across the different watersheds, from stable or increasing, to decreasing and unknown (COSEWIC 2012). |
| Long-Term Trend: | U = Unknown |
| Comments: | . |
| Other Factors | |
| Intrinsic Vulnerability: | B=Moderately vulnerable |
| Comments: |
Bull trout are slow-growing and late-maturing, with a generation time of approximately 7 years (COSEWIC 2012). Bull trout fecundities range from less than 1,000 (stream-resident populations) to up to 9,000 (in anadromous populations; McPhail 2007). |
| Environmental Specificity: | BC=Narrow to moderate. |
| Comments: | Bull trout have a variety of life history patterns (i.e, stream-resident, fluvial, adfluvial and anadromous); however, they are a cold-water species are generally only found in waters less than 15oC (McPhail 2007). |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | |
| Inventory Needs: | |
| Stewardship | |
| Protection: | |
| Management: | |
| Version | |
| Author: | Patricia Woodruff and L. Ramsay |
| Date: | March 23, 2018 |
| References | |
| No references available | |
Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 2018. Conservation Status Report: Salvelinus confluentus pop. 28. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jan 24, 2025).