| Abstract/Description or Keywords |
In 2008, the Fish and Wildlife Compensation Program (FWCP) in partnership with the Habitat Conservation Trust Foundation (HCTF) funded an annual bull trout (Salvelinus confluentus) monitoring program on the Kaslo River. The monitoring program utilized electronic resistivity counters to enumerate out-migrating adfluvial bull trout and traditional redd surveys to provide estimates of spawner escapement in the Kaslo River watershed. The monitoring program builds upon a pilot study conducted in 2006, where the electronic resistivity counts (funded by HCTF) and redd survey counts (funded by FWCP) demonstrated the two independent methods are feasible while providing excellent estimates of escapement. For work conducted in 2008, the main objectives were to 1) utilize two state of the art electronic resistivity counters to enumerate adfluvial out-migrating bull trout 2) conduct redd surveys throughout the watershed, 3) establish an index of abundance for bull trout and 4) establish a standardized population monitoring methodology to assist with conservation and management of bull trout populations in the Kootenay Lake region. In 2008, a redd survey was conducted throughout the entire Kaslo River watershed as part of an ongoing monitoring program for adfluvial bull trout in the Kootenay Lake region. In total, 634 redds were observed over the ~34 km of bull trout spawning habitat in the Kaslo River watershed, a slight increase from 591 redds observed in 2007. This equates to an estimate of 24.4 redds per lineal km on the upper Kaslo River (~20 km), 23.6 redds per lineal km on Keen Creek (~6 km) and < 1 redd per lineal km on the lower Kaslo River (~8 km). An additional redd survey was conducted throughout the entire Crawford Creek watershed in 2008. In total, 181 redds were observed over the ~21 km of bull trout spawning habitat accessible or 8.6 redds per lineal km. This survey included an assessment of all major accessible tributaries to Crawford Creek including; Canyon Creek, Hooker Creek and Houghton Creek. In addition to the redd counts conducted on both systems, electronic restivity counters were used to enumerate migratory bull trout in both systems. One electronic resistivity counter was installed on August 26, 2008 on the upper Kaslo River. However, due to unseasonably high flows, unsuitable site conditions would not permit the installation of a second counter in Keen Creek. An alternative system, Crawford Creek, was identified from some preliminary assessment work done in 2007. Consequently, the second counter was installed in Crawford Creek on September 7, 2008. Results suggested that an estimated 1,197 adult bull trout migrated downstream in the upper Kaslo River in 2008, and an estimated 336 adult bull trout migrated downstream from Crawford Creek system. The estimate on Crawford Creek was not considered a complete count due to the fact the counter was likely installed partly through the downstream migration. Due to the inherent variability (between observers counting redds and identifying true redds) in redd surveys and the concern for their accuracy as an index for monitoring population trends, electronic counters provide the ability to reduce some of the uncertainty as to the number of spawners producing those redds, and thus provide an expansion for the number of fish associated with the number of redds from surveys. Using the electronic counter data for the Kaslo River, it was estimated that there were 2.45 bull trout per redd, slightly above the 2.23 bull trout per redd estimated in 2006. Using an average of 2.3 bull trout per redd, Keen Creek likely supported > 300 bull trout for spawning. Additionally, although not considered a complete count, using the electronic counter data for the Crawford Creek system (~21 km) an estimate of 1.8 bull trout per redd was calculated. However it is likely that this estimate is biased low due to the late installation of the counter. Based on the average of 2.3 bull trout per redd from the Kaslo River, the Crawford Creek system most likely supported an escapement of > 400 fish. In summary, the two methodologies continue to provide valuable enumeration techniques to index adfluvial bull trout within the Kaslo River system. The program indicated that an impressive number of adult bull trout (estimated >1,500) utilized the Kaslo River watershed for spawning in 2008. The high escapement in 2008 continues an increasing trend in the Kaslo River watershed since 2006, based on redd surveys and expansion. Furthermore, 300-400 spawners utilized the Crawford Creek system, indicating another healthy population of adfluvial bull trout within the Kootenay Lake region. This data should assist in increasing our understanding and monitoring of these unique char and how the bull trout escapement relates to the upper trophic level response to the successful nutrient restoration program on Kootenay Lake. |
