Summary report of Bulkley/Morice River steelhead data collected by the Wet’suwet’en Fisheries during the 2010 Moricetown Tagging Project



Since 1999, the Moricetown Salmon Tagging Program 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 Ministry of Environment, Skeena Watershed Initiative, the Pacific Salmon Foundation, and the British Columbia Living Rivers Trust Fund. Since the initiation of this program, the annually collected steelhead data have gained value and importance as the sampling experience and program have developed. 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 2010, steelhead catch at both the campground (N=3510) and at the canyon (N=6323) reached record levels for the second consecutive year. Based on the recapture of 452 steelhead of the 2946 tags that were applied at the campground and the 6323 steelhead that were re-sampled at the canyon, the stratified abundance estimates for steelhead arriving at Moricetown were 33 047 (95% C.I. 29 599 – 36 495) using Maximum Likelihood Darroch (ML Darroch) and 37 851 using Schaeffer estimates, compared to 41 140 (95% C.I. 38 058 – 44 934) using the pooled Petersen estimate that has commonly been referred to for inter-annual comparisons of steelhead abundance in previous years. Although the ML Darroch estimate of 33 047 steelhead may have less bias than the pooled-Petersen estimate due to the heterogeneity of catchability identified among temporal strata in the 2010 data, it is also not as precise and may be an under-estimate. Excluding pooled-Petersen estimates for 1999 and 2000 which had few recaptures and poor accuracy (>50% error), the estimate of 41 140 steelhead arriving at Moricetown Canyon in 2010 is 50% greater than the next highest abundance recorded since 2001 (i.e. 27 484 in 2008).

–Excerpt from the report’s Executive Summary

The appendices to this report can be found here.