FY 2022 Skagit Chinook escapement assessment using Unmanned Aerial Vehicle (UAV)

This project is a stock assessment (i.e., monitoring) project to improve Management of a valuable tribal resource. The project is designed to use unmanned aerial vehicle (UAV) system technology as a complement to helicopter surveys operated by Washington Department of Fish and Wildlife. These methods are implementing aerial spawning surveys to estimate salmon escapements. The present method deploys helicopter flights. The additional UAV missions would help assure full survey coverage during Skagit Chinook spawning period. Ground surveys will also be conducted to ground truth and collect biological data for stock assessment needs.



The proposal would cover the implementation of a 4th year of this continuing project. The UAV missions will be deployed to assess the six Chinook populations on the Skagit River system. The survey river reaches would include the Skagit River, Cascade River, Suiattle River, and Sauk River. Surveys will be implemented once every 10 to 14 days per population as water clarity conditions dictate. Spawning occurs from late July through early November depending on the Chinook population.

Climate Impacts:



Climate and hydrology modeling for the Pacific Northwest is predicting reductions in total snow- pack combined with increased temperatures over the next 50 years (Mote and Salathe 2009). Seasonal hydrology will shift to more severe early storms and more frequent storms throughout winter resulting in increased peak river flow events (Mantua et al. 2009). Glacial till erosion is increasing as Glaciers continue to retreat (Battin et al. 2007). The above-mentioned conditions are decreasing water visibility in the Sauk River due to increased turbidity. The consequence is reduced salmon egg-to-fry survival caused by scouring and/or bed-load blanketing of redds.



It is essential for managers to collect accurate escapement data for Sauk summer Chinook considering the increased environmental impacts to such a vulnerable population. Days for optimal aerial surveys under good water visibility conditions is decreasing during the spawning period. The logistics of booking a helicopter reduces survey opportunities too especially considering flight and river visibility conditions can change within hours. An Unmanned Aerial Vehicle (UAV) can be deployed immediately when good aerial survey conditions are present. We feel the use of a UAV is a sound adaptive management approach to combat climate change impacts that reduce aerial survey data collection opportunities.



Tribal Trust Resources:



The Sauk-Suiattle Indian Tribe has historically fished Chinook salmon in the Skagit River system for commercial, subsistence, and ceremonial benefits. The Bolt decision ruling (United States v. Washington 1974) reaffirmed the tribe’s treaty right that fisheries were a trust resource. The Sauk-Suiattle Indian Tribe was one of the signatories to Treaty of Point Elliot of 1855. Article 5 of the treaty states “The right of taking fish at usual and accustomed grounds and stations is further secured to said Indians in common with all citizens of the Territory”. Supreme Court has ruled that Treaties are to be construed as a grant of rights from the Indians”.



The Skagit Chinook populations are composed of 3 spring populations and 3 summer/fall populations. The spring and summer/fall populations are divided into two separate management units for harvest management purposes. The near-term tribal recovery plan harvest goals are 20,000 summer/fall Chinook (SRSC and WDFW. 2005). There has not been a terminal area commercial summer/fall Chinook fishery in the Skagit River in 8 plus years. A limited subsistence fishery has targeted the Marblemount Hatchery spring Chinook return.



Resource Management:



The federally approved Puget Sound Chinook Harvest Management Plan requires the State and the tribes to develop annual fishing regimes that will assure Chinook populations at least maintain low abundance threshold (LAT) levels on the spawning grounds. This project explores advanced technology to counter the logistic problems with helicopter flights to assure aerial spawning survey monitoring will be maintained to obtain accurate escapement estimates and therefore meet ESA requirements.



The Skagit Chinook Recovery Plan identifies the need of more accurate data for the 6 Skagit Chinook populations. The three Skagit Tribes which includes the Sauk-Suiattle Indian Tribe and Washington State developed the recovery plan.



This project also addresses the Pacific Salmon Treaty strategic research goal to increase our understanding of habitat capacity and production potential particularly for key limiting stocks. Our project focuses on these factors and is applied to Skagit stocks which are included in the list of “stocks of concern” in Annex IV (Chapter 3, Attachments I – V) of the Pacific Salmon Treaty.