. Big Hole River Arctic Grayling Restoration Project annual report : 1992. Arctic grayling. Longth Group (Inclwt) Figure 13. Length-frequency distribution of all grayling captured in Big Hole River electrofishing surveys, Fall, 1992. Younq-of-the-Year We assessed recruitment of YOY grayling during summer and fall population surveys. In spite of low flows, spawning success was relatively high. Number of YOY grayling and capture locations are mapped in Figure 14. Mainstem Big Hole River spawning success was moderate in the McDowell Section and the Squ
. Big Hole River Arctic Grayling Restoration Project annual report : 1992. Arctic grayling. Longth Group (Inclwt) Figure 13. Length-frequency distribution of all grayling captured in Big Hole River electrofishing surveys, Fall, 1992. Younq-of-the-Year We assessed recruitment of YOY grayling during summer and fall population surveys. In spite of low flows, spawning success was relatively high. Number of YOY grayling and capture locations are mapped in Figure 14. Mainstem Big Hole River spawning success was moderate in the McDowell Section and the Squaw Creek area with 42 YOY captured in each in 2 passes. In the McDowell Section the majority of YOY grayling were caught above the diversions. The reach in the vicinity of the Big Hole River's confluence with Squaw Creek appears to provide substantial recruitment. The West Channel of the Wisdom Section was severely impacted by the low flow period of May 18 to May 26, 1992. The peak of spawning activity occurred from April 21 to 24, and densities of spawning grayling was similar in all sections. By interpolating from values given in Kratt and Smith (1977) and Wojcik (1955), we determined that the grayling fry hatched after degree-days, or from May 2 to 4. Kratt and Smith (1977) reported that fry remain in the gravel for 3 days prior to emergence. If so, the grayling should have emerged from May 5 to 7. Upon emerging, grayling fry are relatively undeveloped and require low velocity backwater and stream margin habitats for rearing (reviewed in Armstrong 1986). The extreme low flow due to irrigation withdrawals in the McDowell Section depleted these habitats and hence only 2 YOY were captured in the West channel. An ordinarily productive side-channel of the mainstem Big Hole near the mouth of Doolittle Creek may have been similarly affected by low flows, as only 5 YOY were captured in that vicinity. 22. Please note that these images are extracted from scanned page images that
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