Mitigation for the Construction and Operation of Libby Dam

Keeler Creek
Bull trout that spawn in Keeler Creek (including the North, South and West Forks)
are an adfluvial stock, that migrate downstream out of Bull Lake into Lake Creek, then up
Keeler Creek. This downstream spawning migration is somewhat unique when compared to
other bull trout populations (Montana Bull Trout Scientific Group 1996). Lake Creek, a
tributary of the Kootenai River, has an upstream waterfall barrier isolating this population
from the mainstem Kootenai River population. A micro-hydropower dam constructed in
1916 covered the upper portion of the waterfall. A series of high gradient waterfalls are still
present below the dam, and are barriers to all upstream fish passage. Keeler Creek may
supply some recruitment to the Kootenai River through downstream migration. We observed
a total of 87 bull trout redds in Keeler Creek and associated tributaries in 2003 (Table 1). A
beaver dam located in lower Keeler Creek during late summer/early fall 2001 likely impeded
upstream bull trout migration. The dam was removed, but stream flow increased
substantially after the dam was removed and prevented counts from being made after
removal of the dam. Therefore, the 13 redds observed in 2001 is an underestimate of the true
number of redds in Keeler Creek in 2001. With the 2001 observation included, annual
variation is high (r 2 = 0.004; Figure 9), although the trend is an increasing population trend,
although the relationship is not significantly different from a stable population (Figure 9; p =
0.889). Given this relationship, the annual mean (77 redds) does an equally good job of
prediction. The 2003 observation represents a 13% increase relative to the annual mean.
However, if we remove the 2001 observation from the dataset and repeat the regression trend
analysis, bull trout redds in Keeler Creek show a nearly significant increasing trend since
1996 (Figure 9; r 2 = 0.366; p = 0.150).
120
Bull Trout Redds
100
80
60
40
20
1996-2003
r 2 = 0.0036
p = 0.889
Y = -1351.2 - 0.714*X
2001 Excluded
r 2 = 0.366
p = 0.150
Y = -6998.3 + 3.54*X
0
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Year
Figure 9. Bull trout redd counts and trend line (blue line) in Keeler Creek, a tributary to Lake
Creek, 1996-2003. A beaver dam was present in lower Keeler Creek in the fall of 2001 that
likely impeded bull trout migration. Therefore the 2001 observation was removed and the
regression analysis was repeated (orange line).
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