Strategies for identifying and mitigating predation on salmon in Washington’s “estuaries of concern”

• Main Author: Clark, Dr. Casey
• Format: Text
• Language: English
• Published: Western CEDAR 2022
• Subjects: Ballard; harbor seal; Orca
• Online Access: https://cedar.wwu.edu/ssec/2022ssec/allsessions/203; https://cedar.wwu.edu/context/ssec/article/3365/type/native/viewcontent/SSEC_20Estuaries_20of_20Concern_20Presentation_20__20C._20Clark.pptx_AWSAccessKeyId_AKIAYVUS7KB2I6J5NAUO_Signature_RbCArvXMlagoCcJBrGqs9kw5hrg_3D_Expires_1690453770

Reduced salmon run sizes, fishery closures, and rebounding predator populations have made predation on salmonids by seals, sea lions, and birds a focal point for discussions of salmon conservation and management in the Salish Sea. Predation on threatened and endangered Chinook salmon has been of particular concern and was highlighted by the Southern Resident Orca Task Force as an important subject for further research. Rivers and estuaries are a good place to focus this work, due to elevated predation that can occur at biological pinch points in these systems (e.g., Bonneville Dam, Ballard Locks) and the opportunity to target management to benefit specific salmon runs. Investigation of the timing, location, and intensity of pinniped and avian predation on salmonids in “estuaries of concern” can inform management recommendations to meet the custom needs of an individual watershed. In partnership with the Stillaguamish Tribe, Washington Department of Fish and Wildlife (WDFW) applied these principles to the Stillaguamish River, to better understand the impacts of pinniped and avian predation on different life stages of threatened Chinook salmon in this system. Since April 2021, WDFW has been conducting shore-based surveys to quantify the abundance of potential salmon predators in the river and estuary. Additional pilot work included aerial and boat-based surveys to estimate predator abundance in the outer estuary, harbor seal scat collections for diet analyses, and investigation of scarring on Chinook from predation attempts. Efforts will be expanded in 2022 to include satellite tagging of harbor seals to investigate their use of the river and estuary habitats during smolt outmigration and adult Chinook return. Lessons learned from this project will be used to improve this research model so that it can be applied to other estuaries of concern in Washington to benefit threatened and endangered salmonids, Southern Resident killer whales, and fisheries.