Lower Columbia River Sculpin and Dace Life History Assessment (CLBMON-43). Year 5

Author: A.M.E.C.

This monitoring program was initiated in 2009 and carried out over five years. This project is complete. The main objective of this study was to collect information on the life history, timing, and habitat use of four sculpins (Prickly, Torrent, Columbia, and Shorthead) and two dace (Umatilla and Longnose) species that may be affected by water level fluctuations resulting from daily and seasonal operations of Hugh L. Keenleyside (HLK) dam.

The highest risk of stranding and interference with the normal life cycles of sculpins and dace occurs during the spawning, incubation and early rearing period (May-August in the LCR) for these species. This finding is supported by the current study as well as the broader analysis of CLBMON-42 pool stranding observations (Thorley 2014). Rapid flow reductions between June and August pose the highest risk of stranding for these species when they are actively spawning through to the early rearing period. More rapid decreases during the descending hydrograph phase were observed in 2012 and 2013 in the LCR, but these years also had highest observable flows during the current study. In 2012, LCR water level was influenced by flow reductions from both HLK and the Kootenay River in late July through September, whereas in 2013 it was influenced by a flow reduction from the Kootenay River in June and HLK reductions during July through September (Figure 3). It is suspected that
rapid declines during this period in 2013 caused dewatering of numerous sculpin nests in the LCR (Section 5.6.2.3) and in turn caused 100% embryo mortality; male sculpins guarding nests also became dewatered at this time, but often moved to deeper areas to avoid becoming stranded. Embryo survival may also have been affected by the rapid hydrograph declines in 2012, but low embryo survival was also observed in 2011 and was unrelated to the hydrograph
(Section 5.6.1.2)

The highest risk of stranding and interference with the normal life cycles of sculpins and dace occurs during the spawning, incubation and early rearing period (May-August in the LCR) for these species. This finding is supported by the current study as well as the broader analysis of CLBMON-42 pool stranding observations (Thorley 2014). Rapid flow reductions between June and August pose the highest risk of stranding for these species when they are actively spawning through to the early rearing period. More rapid decreases during the descending hydrograph phase were observed in 2012 and 2013 in the LCR, but these years also had highest observable flows during the current study. In 2012, LCR water level was influenced by flow reductions from both HLK and the Kootenay River in late July through September, whereas in 2013 it was influenced by a flow reduction from the Kootenay River in June and HLK reductions during July through September (Figure 3). It is suspected that
rapid declines during this period in 2013 caused dewatering of numerous sculpin nests in the LCR (Section 5.6.2.3) and in turn caused 100% embryo mortality; male sculpins guarding nests also became dewatered at this time, but often moved to deeper areas to avoid becoming stranded. Embryo survival may also have been affected by the rapid hydrograph declines in 2012, but low embryo survival was also observed in 2011 and was unrelated to the hydrograph
(Section 5.6.1.2)