Abundance and Distribution of Bull Trout in Elk Creek, Alberta 2010


Chad Judd and Mike Rodtka


The majority of Alberta’s bull trout (Salvelinus confluentus) populations, according to
Alberta Sustainable Resource Development, are classified as being ‘At Risk’ or at ‘High
Risk’ of extirpation and therefore require updated abundance information for managers
to monitor population trends. The Clearwater River core area bull trout population is
classified as being at ‘High Risk’ of extirpation. We used single pass electrofishing
capture data from inventory sites, as well as capture-mark-recapture estimates, to
quantify the spatial distribution and abundance of bull trout in Elk Creek, a tributary to
the Clearwater River. From 14 April to 6 May 2010, we electrofished 15 systematically
distributed sample sites, for a total sample distance of approximately 3.7 km of Elk
Creek. Bull trout were captured at 14 of the 15 inventory sites and were the dominant
species in the headwaters. Brown trout were the dominant species in the lower half of
Elk Creek. We captured 135 bull trout that ranged in size from 59 – 326 mm fork length
(FL) but our catch was dominated by juvenile and sub-adult fish and did not include
enough adults (≥250 mm FL; n=6) for valid adult abundance estimates. Estimated
abundance of bull trout (≥70 mm FL) in Elk Creek is 1,031 (95% CI = 827 – 1,327). Bull
trout density was greatest 23 km upstream from the mouth. We used size-at-maturity
information for bull trout from the Clearwater River to determine the approximate size
of adult fish in Elk Creek. Size-at-maturity data from Elk Creek would enable a more
accurate description of adult bull trout abundance in the stream. Our study will provide
resource managers with data required to update the status of Elk Creek’s bull trout
population in the Clearwater River core area.

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