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Mitigation for the Construction and Operation of Libby Dam

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Pipe Creek<br />

Bull trout redd counts in Pipe Creek peaked in 1999 with 36 redds, with redd numbers<br />

<strong>and</strong> have decreased since that peak. Despite <strong>the</strong> decreasing trend <strong>of</strong> bull trout redds during <strong>the</strong><br />

last four years, <strong>the</strong> overall general trend during <strong>the</strong> time period 1995-2003 has been variable,<br />

with a slope that is not significantly different than a stable population (Figure 5; r 2 = 0.149; p =<br />

0.173). The mean number <strong>of</strong> bull trout redds since 1990 has been 15 redds. The 10 redds we<br />

observed in Pipe Creek in 2003 was 33.3% lower than <strong>the</strong> 13 year average. Low water<br />

conditions during <strong>the</strong> fall spawning season during <strong>the</strong> past three years may partially explain<br />

<strong>the</strong> low spawner escapement into Pipe Creek.<br />

Bear Creek<br />

Bear Creek bull trout redd counts have been variable during <strong>the</strong> period 1995-2003<br />

(Figure 6; r 2 = 0.03). Although <strong>the</strong> overall general trend has increased since 1995, <strong>the</strong><br />

relationship is not statistically different than a stable population (Figure 6; p = 0.668). Low<br />

water conditions in Bear Creek during <strong>the</strong> past three years also partially explain <strong>the</strong> low<br />

spawner escapement in Bear Creek. The average number <strong>of</strong> bull trout redds since 1995 in<br />

Bear Creek has been 16.1 redds. The 14 redds we observed in Bear Creek in 2003 was<br />

13.1% less than <strong>the</strong> 8 year average.<br />

O’Brien Creek<br />

The general trend <strong>of</strong> bull trout redds in O’Brien Creek is generally increasing since<br />

1995 (Figure 7; r 2 = 0.592; p = 0.002). We observed a total <strong>of</strong> 46 bull trout redds in O’Brien<br />

Creek in 2003 (Table 1).<br />

West Fisher River<br />

We were unable to determine a significant trend in bull trout redds in <strong>the</strong> West Fisher<br />

River over <strong>the</strong> period <strong>of</strong> record <strong>for</strong> this stream (1993-2003). From <strong>the</strong> period 1993-2000, <strong>the</strong><br />

general trend was one <strong>of</strong> increasing abundance. However, we observed only 1 bull trout redd in<br />

each <strong>of</strong> <strong>the</strong> previous three years (Figure 8). The overall trend was not significantly different<br />

than a stable (zero slope) population (r2 = 0.036; p = 0.578). Given <strong>the</strong> amount <strong>of</strong> variation<br />

present within this dataset, <strong>the</strong> overall mean number <strong>of</strong> redds in <strong>the</strong> West Fisher (mean = 5.6<br />

redds) does an equally good job at predicting redd numbers. Drought conditions during <strong>the</strong><br />

previous 3 summers/late fall periods may have contributed to <strong>the</strong> lower bull trout spawner<br />

escapement into <strong>the</strong> West Fisher River.<br />

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