CRITFC Columbia River Basin Predation

Snake River spring and summer Chinook, upper Columbia River steelhead, and middle Columbia River steelhead are among some of the listed stocks that are most impacted by double crested cormorants throughout the Columbia River basin. The greatest impacts are found in the Columbia River estuary, specifically from Bonneville Dam to the Pacific Ocean.



In the period from 2003 to 2013, the East Sand Island colony of double crested cormorants were estimated to conservatively consume an average of 11+ million smolts annually, this figure exceeding 15+ million smolts from 2010-2013 (DEIS 2015). Species consumed included steelhead, sockeye, Chinook, and coho salmon smolts. The greatest impacts are found in the Columbia River estuary, specifically from Bonneville Dam to the Pacific Ocean, as the smolts in this section of the river have passed up to 8 major hydroelectric projects and hundreds of miles of reservoirs, they are the survivors.



Beginning in 2015 and continuing Federal managers attempted to manage this population 2015 -2020 using a combination of lethal take, egg oiling and habitat reduction. The management action did reduce the population substantially, but since 2020, the remaining birds have shifted their location upstream from East Sand Island to locations that are mixed salt and freshwater (i.e. mixing zone) and wholly freshwater further upstream. The prey base of double crested cormorants becomes less diverse from salt water to the mixing zone to freshwater. In the freshwater zone, the prey base is dominated by outmigrating smolts from March through June. The mixing zone of fresh and salt water now has over 5000% more birds that it did prior to the management action, and the totally freshwater section of the estuary has 349% increase in double crested cormorants.



Double crested cormorants in the mixing section of the estuary consume 4.3 times as many smolts as those in the saltwater portion of the estuary, while the population in the freshwater section consume over 8 times the number of smolts as double crested cormorants in the saltwater section of the estuary. This shift in numbers of double crested cormorants upstream from the salt water to the mixed and freshwater sections of the estuary has resulted in predation rates that equate to over 26,000 double crest cormorants living the saltwater portion of the estuary (James Lawonn, ODFW, NPCC Presentation Nov 15, 2022).



The focus of this project is to greatly reduce the impact on listed salmonids in the freshwater and mixing zones of the estuary by non-lethal hazing and lethal take of double crested cormorants. Lethal take has previously been authorized by the USFWS (ROD 2020) to reduce the numbers of double crested cormorants in areas where they are impacted both resident and anadromous fish species of importance to tribes and states



Worksite #1 Proposed Work: This project site (Worksite #1) encompasses the freshwater and mixing areas of the Columbia River, specifically from RM 14 (Astoria Megler Bridge) to RM 146 (Bonneville Dam). More specifically, it will focus on specific sites known to harbor double crested cormorants during the spring smolt outmigration. Worksite #1 will remain the same during the entire project. Prior to implementing the Plan, staff will complete paperwork for lethal take permits, will identify double crested cormorant locations and map the sites, locate boat launches, , develop non-lethal hazing plans, a monitoring plan to document bird behavior and implement the non-lethal hazing. Where hazing proves to be in-effective, those locations will become the focus of lethal take efforts. This will be a multi-year effort, with 2023 focused on mapping site locations, acquiring permits, coordinating with USFWS on take numbers, etc. Hazing and take efforts would occur in 2024 -2026, or until funds are exhausted.

The hazing and potential removal of double crested cormorants from the freshwater and mixing zones of the Columbia River estuary will reduce the number of these predators in this section of the Columbia River, thereby reducing the consumption of smolts by double crested cormorants in these sections of the Columbia River; a reduction in the number of double crested cormorants, increased numbers of smolts not consumed by double crested cormorants.