Abundance and Distribution of Bull Trout in Elk Creek, Alberta 2010
Author(s)
Chad Judd and Mike Rodtka
Summary
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.