Why It Matters

A Congressional Research Service report updated June 5 focuses on one of the Pacific Northwest's most intractable wildlife conflicts. Sea lion predation on Columbia River salmon and steelhead trout is forcing Congress to choose between two of its own landmark environmental laws.

The Marine Mammal Protection Act (MMPA) and the Endangered Species Act (ESA) are pulling in opposite directions. Sea lions, whose populations have grown substantially since the MMPA's 1972 enactment, are consuming federally protected salmon and steelhead at a scale that threatens recovery efforts for 13 salmon runs listed as threatened or endangered in the Columbia River Basin. Neither law yields easily to the other, and the tools Congress has provided to manage the tension have proven difficult to deploy at scale.

The Big Picture

The Columbia River wildlife conflict has been building since the 1990s, when sea lion presence near Bonneville Dam began drawing federal attention. The dam, 146 miles above the mouth of the Columbia, creates a natural concentration point for migrating fish, and for the predators that follow them.

Estimated consumption near Bonneville climbed from roughly 1,010 salmon in 2002 to a peak of 10,859 in 2015, representing 4.5 percent of the salmon run that year. By 2016, the percentage reached 6.2 percent even as raw numbers began to fall. Since then, consumption estimates have declined to about 2.8 percent of the run in 2024. The CRS report cautions that post-2019 data comes from shorter sampling windows and may not be directly comparable to earlier figures.

California sea lion populations are currently estimated by the National Oceanic and Atmospheric Administration's National Marine Fisheries Service (NMFS) to be within the range of their optimum sustainable population. The eastern population of Steller sea lions was delisted from the ESA in 2013 and is also assessed to be near its optimum sustainable population. Wild salmon run sizes, by contrast, remain a small fraction of historic levels.

Congress has twice intervened to expand removal authority. In 1994, it authorized the Secretary of Commerce to issue permits to states for lethal removal of sea lions that negatively affecting salmon recovery. In 2018, the Endangered Salmon Predation Prevention Act provided additional flexibility for state and tribal entities to remove sea lions in specific Columbia River segments, including a five-year renewable permit mechanism. States of Washington, Oregon, and Idaho, along with tribal parties, have carried out lethal removals primarily near Bonneville Dam and Willamette Falls under these authorities.

Nonlethal deterrence, such as pyrotechnics, water spray, rubber bullets, boat chases, and physical barriers, has been deployed extensively. Scientific reviews cited in the report find these measures are often ineffective in the long term, as sea lions adapt to or ignore them, or return after being transported elsewhere.

In 2025, NMFS renewed the five-year lethal removal permit, authorizing the take of up to 424 California sea lions and 62 Steller sea lions through August 2030. Historically, actual removals have run below authorized limits.

Political Stakes

For the Administration

The Oregon Department of Fish and Wildlife and other state agencies have argued that lethal removal is effective and that failing to address Pacific Northwest fish predation will constrain not just salmon recovery but also power generation from Columbia River hydropower facilities. Linking salmon management to energy output carries weight in an administration focused on reducing regulatory friction around energy production.

At the same time, the Mammal Commission has concluded that where the MMPA and ESA conflict, the statute directs that conservation of ESA-listed salmon stocks takes precedence over protection of individual sea lions from healthy populations. That legal interpretation, if consistently applied, would support more aggressive removal. But other stakeholders have pushed back, arguing that climate change, hydropower infrastructure, habitat fragmentation, and disruptions to the food web (including availability of herring prey) are driving salmon population decline in ways that lethal sea lion removal cannot address.

For Democrats

Two constituencies are in opposition, namely tribal nations with treaty-protected fishing rights who have supported lethal removal as part of an integrated management approach, and environmental groups skeptical that culling sea lions addresses root causes of salmon decline. Tribal parties are co-authorized under the current removal permit, giving Indigenous fishing interests a direct stake in how the policy is administered.

For Republicans

The report offers a potential vehicle for broader ESA and MMPA reform. The sea lion-salmon conflict is a concrete, documented case where two federal statutes produce contradictory management obligations, signaling that the congressional committee process is likely to revisit Section 120 of the MMPA.

For the Public

Particularly in Washington, Oregon, and Idaho, the stakes are economic and cultural. Spring Chinook salmon and winter steelhead are the primary species consumed near Bonneville Dam during the January-through-May predation window. Their decline affects commercial and recreational fishing industries, tribal subsistence and ceremonial practices, and the broader ecological health of one of the continent's most significant river systems.

The Bottom Line

The core problem is that neither the MMPA nor the ESA was designed with the other in mind, and decades of amendments have produced a management system that is procedurally burdensome and scientifically contested. Lethal removal is authorized but underutilized. Nonlethal deterrence is widely deployed but largely ineffective over time. The 2025 permit renewal extends existing authority through 2030, but does not resolve the underlying tension. Whether Congress streamlines removal procedures, invests in further data collection as the Marine Mammal Commission has recommended, or pursues broader statutory reform, will determine if the current framework can keep pace with the ecological reality on the Columbia River.

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