Water Stewardship Information Sources

Citation Schubert, ND et al. 2007. Status of Birkenhead River Chinook Salmon (Oncorhynchus tshawytscha). Canadian Science Advisory Secretariat Research Document 2007/019. Department of Fisheries and Oceans.
Organization DFO
URL http://www.dfo-mpo.gc.ca/CSAS/Csas/DocREC/2007/RES2007_019_e.pdf
Abstract/Description or Keywords Birkenhead River Chinook (Oncorhynchus tshawytscha) is a Fraser spring run population
that spawns in a tributary of the Harrison-Lillooet River system in southwestern BC. It is a
genetically isolated population that possesses local adaptations (e.g., far north marine
distribution and very early spawner migration) that are an important component of the
evolutionary legacy of the species.
Population status is assessed by evaluating spawner abundance and trends relative to
potential benchmarks, fishery harvest and potential limiting factors and threats. This
required the reconstruction of escapement and terminal fishery catch estimates based on
a reevaluation of historic data and the inclusion of recent data. The spawner population
has been trendless over a thirty year period when both enhancement was attempted and
conservation actions were applied to the fisheries. The spawner population averaged 480,
with an effective population size of about 300; both are below literature estimates for
viable, genetically isolated populations. Potential benchmarks are discussed, with the
lowest (Ŝmsy = 1,700) over triple current abundances, suggesting that considerable
population growth is required.
Small populations are especially vulnerable to threats such as those posed by fishery
exploitation, climate change and habitat alteration. The Birkenhead has been harvested at
about 50%, with three fisheries predominant: Alaska troll and the First Nations fisheries in
the lower Fraser and Lillooet System. The impacts of climate change are already
apparent in freshwater and are expected to increase in future decades, while the threat
from habitat alteration, geomorphic processes and rapid human population growth remain
significant. A comprehensive recovery plan is required.
Information Type report
Regional Watershed Howe Sound & Sunshine Coast
Sub-watershed if known Birkenhead River
Aquifer #
Comments
Project status complete
Contact Name
Contact Email