Yakama Nation Columbia River Basin Predation IV

Anthropogenic impacts to the Columbia River and its tributaries have altered the habitat and environment to favor many species of salmon predators including piscivorous colonial waterbirds (e.g. California gull, American white pelican, Double-crested Cormorant) and native and non-native predatory fish (e.g. Northern Pikeminnow, Smallmouth Bass and Walleye). We recognize that predation is a keystone agent that controls fish population dynamics. Although predation can be a naturally occurring control mechanism for fish populations, predation management is needed in an altered system like the Columbia River Basin. Research over the last three decades has shown an alarming increase in predation on salmonids. As part of the commitment of the Yakama Nation to honor, protect, and restore our sacred fish and water resources, we will continue to make positive strides in predation research and population management to increase survival of salmon and steelhead.



This is the 4th iteration of a project to manage predation on salmon at sites including the Lower/Middle Columbia Basin, Dalles Reservoir of the Columbia River, Lower/Middle Yakima River, and the Klickitat River Delta.



Worksite #1 Proposed Work:

Miller Rocks in The Dalles Reservoir – Avian dissuasion and depredation activities under this proposal will occur at and around Miller Rocks Islands with the objective of eliminating California gulls, Ring-billed gulls, and other colonial water birds from colonizing and breeding on this culturally and environmentally sensitive area (PCSRF funds).



Worksite #2 Proposed Work:

Lower/Middle Yakima River –During the salmon smolt migration, we will lethally remove 156 American white pelicans (PCSRF funds) and analyze diet composition (non-PCSRF funds). Aerial flights will be conducted to determine pelican abundance and distribution within the Yakima River (PCSRF & non PCSRF funds) to help focus future efforts. Supporting CTUIR trapping and satellite tagging of pelicans (PCSRF & non PCSRF funds).



Worksite #3 Proposed Work:

Klickitat River Delta – We plan to provide additional support (PCSRF funds) for predator removal including bank and boat-based hook and line sampling and/or seining and electrofishing (non-PCSRF funds). This support may include planning, permitting and on the ground removal efforts building upon ongoing work to investigate species composition, abundance and distribution in the Klickitat River delta focusing on predator species both native and non-native.



Worksite #4 Proposed Work:

Middle/Lower Columbia River Basin -- Assist YNF/CRITFC/USACE/CTUIR or other avian managers with dissuasion, depredation, or research (PCSRF funds) within the Columbia River basin to reduce predation on salmonid smolts.

Avian predation is one of the largest sources of hydro-system mortality for juvenile steelhead and Chinook salmon (Evans et al., 2022). In 2021, the predation/consumption rate of juvenile Upper Columbia River steelhead and Snake River sockeye at Miller Rocks alone was 12.4% and 13.9% respectively (Evans et al., 2022). Estimates of smolt consumption rates by gulls nesting at Miller Rocks in The Dalles Reservoir were the highest of any colony evaluated in 2021 (Evans et al., 2022), yet the Miller Rocks gull colony and most colonial waterbird populations are currently unmanaged. Miller Rocks is located within the Yakama Nation Territories and was created by the construction of The Dalles Dam. Miller Rocks is a culturally important location for the Yakama Nation Tribal members; removing the gull colony is a top priority for the Yakama Nation and will increase survival of migrating juvenile salmon and steelhead in the reach.



The American white pelican population within the Columbia River basin established in the early 1990s and grew exponentially at Badger Island for two decades. This population is also currently unmanaged and is directly responsible for significant impacts to Yakima River salmon smolts. In 2024 Yakama Nation began the three year diet study and preliminary results suggest more than 25% of a pelican’s diet in the spring is salmonid smolts (spring, summer and fall Chinook, Coho, Sockeye, and Steelhead) and they may consume more than 2 million smolts annually in the Yakima River (USGS, unpublished). This diet study will inform managers in the development of an American white pelican management plan and further protect salmon and steelhead, if necessary, through future management actions.



These extremely high consumption rates of gulls at Miller Rocks and pelicans in the Yakima River result in a direct economic loss to tribal fishers as adult salmon returns decrease. The total economic loss to tribal members is not easily quantified, but the loss and ability to fish at usual and accustomed places due to bird predation is a cultural loss that is far greater than its economic value.



Predator dissuasion and removal has a demonstrated effect on reducing predation rates and increasing survival of salmon and steelhead smolts. Given the high predation rates in these locations we would expect to see a commensurate increase in salmon survival from the Yakima River to McNary dam and within The Dalles reservoir, in direct response to the actions for which we are seeking funding.



Predation by non-native invasive piscine predators (e.g. smallmouth bass, walleye) similarly has disproportional impacts on rearing and migrating salmon stocks. Habitat changes in the Columbia River associated with hydroelectric impoundments have altered the riverine habitat into a series of lacustrine systems creating areas that are now more suitable for both native and non-native predators. Increasing water temperatures has also allowed piscine predators to expand their range into critical salmon rearing habits.



The Yakama Nation has documented disproportionality low survival rates of salmon and steelhead in the lower 1.5 km of the Klickitat River (Romero and Kuhn, 2021). Water velocities through this reach are drastically reduced by backwater effects which in turn increase smolt travel time and greatly increased predation risk and vulnerability to piscivorous predators (Rieman et al., 1991). After fish composition and abundance data is collected in the lower Klickitat River delta and reservoir influenced reaches, we can assess potential predation impacts on salmonid species and inform manager’s decisions on how to improve survival of juvenile salmon migrating from the Klickitat River and manage these piscivorous fish species.