Cowichan River Chinook Salmon Incubation Assessment, 2005–2006 Prepared For Pacific Salmon Commission 600 - 1155 Robson Street Vancouver, BC V6E 1B5 (604) 684-8081 July 14, 2006 By D.W. Burt1 and E. Ellis2 2 1 D. Burt and Associates Kerr Wood Leidal Associates Ltd. 2245 Ashlee Road 200 – 4185A Still Creek Drive Nanaimo, BC, V9R 6T5 Burnaby, BC, V5C 6G9 (250) 753-0027 (604) 294-2088
[email protected] [email protected] EXECUTIVE SUMMARY This purpose of this study was to determine whether upstream sediment sources are adversely affecting egg-to-fry survival of Cowichan River chinook salmon. This information is necessary to determine whether remedial action to eliminate/diminish these sediment sources is warranted to assist in the recovery of Cowichan River chinook stocks. The specific objectives of the study were to: 1) monitor suspended sediment levels above and below known point sources at various flows during the 2005-2006 winter, 2) determine the level of fine sediment in selected spawning sites above and below the major sediment sources, 3) assess incubation survival by in situ trials and by hydraulic sampling at selected spawning sites above and below the major sediment sources, and 4) undertake a literature review on the effects of fine sediment on egg-to-fry survival. Suspended sediment levels were monitored by taking in situ turbidity measurements and by collecting water samples for lab analysis of total suspended solids (TSS). Substrate composition of spawning beds was assessed by collection of sediment samples at 1 site above the sediment sources (control) and 2 sites below the sediment sources (test sites).