Kaslo River and Crawford Creek Bull Trout Spawner Assessment 2009
Authors:
Greg Andrusak
Year:
2010
Report Abstract
During August 2009 resistivity counters were placed on the lower portions of the Kaslo River and Crawford Creek in an effort to record downstream movements of spawned out adfluvial bull trout that inhabit Kootenay Lake. Upstream movement of spawners was recorded as soon as the counters were operational and a peak of upstream movement on the Kaslo River was recorded in mid September. The Crawford Creek counter suggested that the peak of upstream movement was earlier in August as far fewer fish were recorded moving upstream compared to downstream numbers. Run timing was well defined by the counters and the peak of spawning was determined after downstream movement increased at the end of September. This informaitno signaled the timing of redd surveys on both systems that were conducted in the first week of October.
The redd survey on the Kaslo River estimated a total of 689 redds of which 542 were observed in the upper Kaslo River, 139 in Keen Creek and the remaining 8 redds were counted between the counter and downstream to the lake a distance of approximately 8 km. Redds per km were 27/km for the Kaslo River, 23/km in Keen Creek and 1.0/km in the main river below the counter. The survey on Crawford Creek counted a total of 268 redds with the majority (n=233) observed in the mainstem while the balance were located in the lower reaches of three tributaries. Redd densities were much lower in Crawford Creek compared to the upper Kaslo River with 11 fish/km in the mainstem and a range of 10-31/km in the three tributaries.
The Kaslo River resistivity counter recorded a total of 1,219 spawners while the Crawford Creek count was 486. Comparing the 2009 redd counts to the counter numbers results in a conversion factor of 2.2 fish/redd for the Kaslo system and 1.8 fish/redd for Crawford Creek. The differences between the two systems are attributed to far greater amounts of suitable spawning habitat in the upper Kaslo River compared either Crawford or Keen creeks. The derived expansion factors could be applied to other tributaries where resistivity counters cannot be operated but redd surveys are feasible.
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