| Citation |
Saimoto, Ron S.; Saimoto, Regina K. (2012) Summary report of Bulkley/Morice River steelhead data collected by the Wet’suwet’en Fisheries during the 2011 Moricetown Tagging Project, SKR Consultants Ltd. Prepared for Ministry of Forests, Lands and Natural Resource Operations and Pacific Salmon Foundation, The Living Rivers Trust Fund. |
| Abstract/Description or Keywords |
Since 1999, the Moricetown Salmon Tagging Project has been conducted on the Bulkley River by the Wet’suwet’en Fisheries and Fisheries and Oceans Canada, with the inclusion of data collection for steelhead (Oncorhynchus mykiss) under assistance from the British Columbia Smithers Fisheries Office, the Pacific Salmon Foundation, and the British Columbia Living Rivers Trust Fund. This mark and recapture project has involved sampling by beach seine for tag application immediately downstream of Moricetown Canyon (i.e. referred to as “campground”) and re-sampling by dip net at the base of Moricetown Falls and fishway (i.e. referred to as “canyon”). In 2011, steelhead catch at both the campground (N=1 131) and at the canyon (N=2 896) were relatively good in comparison to the earlier years of this study, but somewhat lower than the previous year (i.e. 2010) as a result of fewer steelhead arriving and reduced sampling effort due to high river levels. In total, 2896 steelhead were examined at the canyon, including 140 recaptures of the 931 steelhead tagged at the campground. The stratified abundance estimates for steelhead arriving at Moricetown with a 2.5% correction for tag loss were 18 199 (95% C.I. 13 692 – 22 707) using Maximum Likelihood Darroch and 18 770 using Schaefer methods. The stratified abundance estimates are provided to identify potential inaccuracies, bias and misleading precision of 19 149 (95% C.I. 16 709 – 22 725) using the pooled Petersen estimate for inter-annual comparisons of steelhead abundance in previous years. In general, the pooled Petersen estimate for steelhead abundance in 2011 appears to be in the lower range in comparison to previous years and is less than half and significantly lower than the highest and most precise estimate of steelhead arriving at Moricetown in 2010 (i.e. 41,140 with 95% C.I.: 38,058 – 44,934). Some manipulations of the pooled-Petersen estimates have been included to represent the number of steelhead that actually migrated upstream of Moricetown Canyon as of the final date of sampling at the canyon in comparison to the estimate of steelhead that arrived at the campground. Based on the 2009 acoustic telemetry study estimating 34% of steelhead that arrived at the campground but did not migrate upstream of Moricetown Canyon while the dipnet fishery was operating (Welch et al. 2009 & 2010), a range of rates of fallback (i.e. 10%, 20% and 40%), have been used as examples of the range of adjustments suggested to estimate steelhead abundance upstream of Moricetown. The corrected pooled-Petersen estimates for steelhead migrating upstream of Moricetown are suspected to be 17 234 with 10% fallback, 15 319 with 20% fallback, and 13 804 with 40% fallback of steelhead that were tagged at the campground and predicted not to have migrated past the canyon as of October 13th in 2011. |
