Spawning Demographics of Bull Trout in the Upper Red Deer River Drainage, 2009-2011
Insufficient information on the abundance, life history strategy and spawning demographics of bull trout (Salvelinus confluentus) in the upper Red Deer River drainage complicates management of this species. Coupled with the lack of information, are impacts on bull trout from increased land use and recreational angling in the drainage. We conducted a three-year study of the abundance, life history strategy and spawning demographics of bull trout in the upper Red Deer River drainage. In the first program year (2009), we investigated the abundance of juvenile/resident bull trout and spawning use in Pinto Creek, in our second year (2010), we assessed the magnitude and timing of bull trout spawning in Pinto Creek and also assessed spawning use in other prioritized streams in the upper Red Deer River drainage, and in our third year (2011), we assessed the magnitude and timing of bull trout spawning in Sheep Creek.
In 2009, we captured 85 bull trout in Pinto Creek with backpack electrofishing gear. Estimated total bull trout abundance was 4,714 (95%CI = 1,644–14,916), and the adult resident bull trout (fish ≥ 250 mm fork length) abundance was 413 (95%CI = 146–1,024). We documented 56 bull trout redds in 13 km of Pinto Creek, indicating its importance as a spawning stream.
In 2010, we captured 43 adult bull trout in Pinto Creek using a fish trap, 8 moving upstream from North Burnt Timber Creek into Pinto Creek and 35 migrating downstream out of Pinto Creek. We also documented 17 bull trout redds in 8 km of Sheep Creek, indicating its importance as a spawning location.
In 2011, we captured 41 bull trout in Sheep Creek using backpack electrofishing gear. Estimated total bull trout abundance was 1,097 (95%CI = 384–3,648), and the adult resident bull trout abundance was 198 (95%CI = 72–489). We captured 7 bull trout moving upstream through our fish trap on Sheep Creek and 17 bull trout moving downstream. We documented 68 redds in Pinto Creek and 44 redds in Sheep Creek, confirming their importance as bull trout spawning streams.
At nine microsatellite DNA loci studied, brook trout (S. fontinalis) alleles were found in 3.4% of bull trout. This is evidence of low-level hybridization and this introgression of brook trout genes into bull trout populations should be monitored.