Characterizing Contaminant Concentrations in Priority Chinook Salmon Stocks Consumed by Resident Killer Whales in the Northeastern Pacific Ocean

• Main Author: Holbert, Stephanie
• Format: Text
• Language: English
• Published: Western CEDAR 2022
• Subjects: Albion; British Columbia; Canada; Fraser River; Pacific; First Nations; Killer Whale; Orca; Orcinus orca; Killer whale
• Online Access: https://cedar.wwu.edu/ssec/2022ssec/allsessions/156; https://cedar.wwu.edu/context/ssec/article/3318/viewcontent/175_803beca62705489f867bd43784d7e2e9.pdf

The critically endangered, transboundary Southern Resident Killer Whale (SRKW) (Orcinus orca) population faces significant threats including a reduced abundance of their primary prey (Chinook salmon, Oncorhynchus tshawytscha), physical and acoustic disturbance, and high levels of endocrine disrupting contaminants. However, the sympatric Northern Resident Killer Whales (NRKW) that also primarily consume Chinook salmon have had continued population growth and have lower contaminant burdens. Studies have reported adverse health effects from contaminant burdens in transient killer whales and NRKWs. Contaminant exposure modeling has predicted protracted health risks for both resident killer whale populations. Despite Chinook salmon from the Fraser River watershed in British Columbia, Canada compromising up to 90% of the SRKW diet during the summer months, little contaminant information exists for these priority stocks, as well as other priority Chinook stocks from other Canadian rivers. Characterizing contaminant concentrations in SRKWs is exceedingly difficult due to their small population size, endangered status, and long-range habitat movements. Chinook salmon can be used as a proxy for helping to characterize contaminants and their risks to SRKWs. In the current study, muscle tissue from nine priority Chinook stocks consumed by SRKWs and NRKWs were assessed for concentrations of five priority contaminants classes (PCBs, PBDEs, OCPs, Dioxin Furans, and Chlorinated paraffins) and stable isotope (d13C, d15N, d34S) profiles. This enabled the characterization of contaminants in priority Chinook stocks and allowed for a preliminary assessment of exposure between two sympatric resident killer whale populations. Collections were done via partnerships with First Nations, recreational and commercial anglers, and the Albion test fishery. Stable isotopes and stock migrations were used to investigate variables affecting differences in the accumulation of contaminants. This evaluation of contaminants found in resident killer ...