Wahleach Project Water Use Plan Wahleach Reservoir ... - BC Hydro

sticklebacks in 2004 and 2005, were 2.5 fish·net hr (Fig. 20), which was similar to
values measured in 1997 but less than the peak CPUE in 1999 of approximately 6
fish·net hr. The CPUE for sticklebacks in 2006 was 0.41 fish·net hr, lower than
catches found in the spring of 2004 and 2005 but similar to catches in 2000 and
2003 (Fig. 20).
Catch Per Unit Effort
(# Fish·Net Hour -1 )
10
8
6
4
2
0
Threespine Stickleback
Spring
Fall
yr1997 1998 1999 2000 2003 2004 2006
Figure 20. Gillnet catch per unit effort (CPUE) in the spring and fall of threespine
sticklebacks in Wahleach Reservoir, June 1997-2005.
The mean fork length and mean weight of threespine sticklebacks decreased during
each successive year of the sampling period (Fig. 21). Mean fork length decreased
14% to 44.6 ± 1.37 mm in 2005 and 24% to 39.2 ± 0.48 mm in 2006 relative to 2004
values. Weights were not recorded in 2005 but in 2006 the mean weight of
stickleback decreased by 61% relative to 2004 weights (Fig. 21). This suggests that
either food availability was poor, recruitment was poor or that piscivorous predators
are selectively grazing the larger sticklebacks, and causing a shift in the size
distribution to smaller sticklebacks.
Wahleach Reservoir Fertilization Project, 2004-2006.
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