Research Document 2023/042

Recovery Potential Assessment for Southern British Columbian Chinook Populations, Fraser and Southern Mainland Chinook Designatable Units (1, 6, 13 and 15)

By Dionne, K., Rachinski, T., Parken, C., Weir, L., Doutaz, D., Ritchie, L., Bailey, R., Jenewein, B., Miller-Saunders, K., Labelle, M., Manson, M., Welch, P., Trouton, N., Mozin, P., and Walsh, M.

Abstract

Four Southern British Columbian Chinook Salmon (SBCC) (Oncorhynchus tshawytscha) Designatable Units (DU) were assessed as Threatened or Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2020 and are currently under consideration for addition to Schedule 1 of the Species at Risk Act (SARA). The first half of the Recovery Potential Assessment (RPA) (Elements 1-11) first provides descriptions and status updates for the populations, an overview of biology and habitat requirements, and an assessment of the threats and factors limiting recovery. The major threats impacting DUs were assessed in a workshop with local experts and were determined to be climate change, natural system modifications, fishing, and pollution. All four DUs are considered to be at an extreme threat risk due to the severity and number of threats these DUs are facing. Based on the assessed threats, a population level decline of 71% to 100% is expected for DUs 1, 6, 13 and 15. Alleviating the multiple and complex threats to these DUs will be difficult, especially as many of the threats are exacerbated by climate change. The second half (Elements 12-22) provides potential recovery targets, a discussion of mitigation measures, population projections and a recommendation of allowable harm. Survival and recovery targets for each DU were suggested based on Wild Salmon Policy (WSP) benchmarks, with additional requirements about observed percent change in spawners. Data limitations from incomplete escapement coverage and unknown hatchery influences prevented many quantitative assessments and no modelling was completed. The risks imposed by climate change and continued anthropogenic development add additional uncertainty that was only described qualitatively. Based on the qualitative assessment for all four DUs, further harm may continue to jeopardize recovery. Therefore, to promote the survival and recovery of these DUs, it is recommended that all future and ongoing human-induced harm should be prevented so as not to jeopardize recovery. It is important to note that some activities in support of survival or recovery could result in harm but may have a net positive effect on the population and should be considered.

Research Document 2023/042 (PDF, 5,187 KB)

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