Salmon and steelhead are anadromous fish, meaning they are born in freshwater, migrate to the ocean to mature, and return to their place of birth to spawn. Dams and their operations make the migrations treacherous both up and downstream. Federal dams have had an effect on salmon and steelhead populations in the Columbia Basin since the 1938 construction of Bonneville Dam, the first dam in the Federal Columbia River Power System (FCRPS). FCRPS now includes federal hydropower dams in the Columbia Basin that are operated by either the Army Corps of Engineers (Corps) or Bureau of Reclamation (Reclamation). (See Figure 1 .) Electric power from these projects is marketed by Bonneville Power Administration (BPA). Currently, eight evolutionarily significant units (ESUs) of salmon and five distinct populations segments (DPSs) of steelhead in the Columbia Basin are listed as threatened or endangered under the Endangered Species Act (ESA). The ESA-protected fish in the Colombia River Basin are Snake River sockeye salmon (endangered); Snake River spring/summer-run Chinook salmon (threatened); Snake River fall-run Chinook salmon (threatened); Snake River basin steelhead (threatened); Upper Columbia River spring-run Chinook salmon (endangered); Upper Columbia River steelhead (threatened); Middle Columbia River steelhead (threatened); Lower Columbia River Chinook salmon (threatened); Lower Columbia River coho salmon (threatened); Lower Columbia River steelhead (threatened); Columbia River Chum salmon; (threatened); Upper Willamette River Chinook salmon (threatened); and Upper Willamette River steelhead (threatened). The National Marine Fisheries Service (NMFS) of the Department of Commerce has found that the estimated "current annual salmon and steelhead production in the Columbia River Basin is more than 10 million fish below historical levels, with 8 million of this annual loss attributable to hydropower development and operation." Additionally, timber management and grazing have decreased habitat from "approximately 21,000 miles (33,600 km), historically, to approximately 16,000 miles (25,600 km) in 1990, largely due to management practices on U.S. Forest Service (USFS) land." Today salmon and steelhead trout in the Columbia River Basin are a mixture of wild fish and those produced in fish hatcheries. Experiments with artificial propagation of salmon to bolster faltering wild stocks began in the late 1800s. Dozens of federal- and state-managed salmon and steelhead trout hatcheries in the Columbia River basin produce more fish annually than do wild stocks. The ESA requires federal actions, such as FCRPS operations, to be reviewed to determine whether they are likely to jeopardize the continued existence of threatened and endangered species or damage the species' critical habitat. This process is called consultation . By statute, the Secretary of the Interior administers the consultation process, but it has delegated its authority to either NMFS or the U.S. Fish and Wildlife Service (FWS) (in the Department of the Interior ). With regard to protected anadromous salmon and steelhead in the Columbia Basin, NMFS has administrative authority over the consultation process. Thus, if the actions of a federal agency might adversely affect listed salmon or steelhead, they must engage in the consultation process with NMFS. The Corps, Reclamation, and BPA are the action agencies for purposes of operating the FCRPS and the consultation process under the ESA. Formal consultation is initiated when an action agency submits a biological assessment to NMFS describing the proposed action and its impact on listed species. ESA consultation may be triggered by new ESA listings or new or changed federal actions. In the case of salmon and steelhead, NMFS considers the biological assessment and the proposed federal action and then issues a biological opinion (BiOp) indicating whether the action would jeopardize protected species. In developing a BiOp, NMFS must determine whether the action agencies' conduct will likely jeopardize a listed species or destroy or adversely modify its critical habitat. If jeopardy is found, NMFS is required to include reasonable and prudent alternatives (RPAs) to the proposed action in order to avoid jeopardy, provided such alternatives are possible. In those cases where NMFS concludes that the action agencies' conduct as originally proposed or as modified by RPAs is not likely to result in jeopardy or adverse modification or destruction of critical habitat, NMFS will issue an Incidental Take Statement to the action agencies. The Incidental Take Statement excuses any takes (killing or harming) of listed species for operations covered in the BiOp so long as the action agency complies with the terms and conditions of the statement. Without the BiOp and the Incidental Take Statement, the action agency risks violating (and being prosecuted under) the ESA. In addition to BiOps for FCRPS operations, NMFS issues salmonid BiOps for Upper Snake River activities and harvest operations (fishing). The configuration and operation of the FCRPS dams can be a polarizing issue for proponents of hydropower development, irrigation, and river navigation and those who support commercial, sport, and tribal fishing as well as environmental conservation. Commentators note that Columbia Basin salmon populations have declined due to a number of human actions besides FCRPS operations, including fishing, predation by native and invasive species, water pollution, reduced habitat, and water withdrawals for irrigation. Many also assert that these populations will be subject to increasing stress from factors related to climate change such as higher water temperatures, changes in ocean conditions, and lower river flows. Actions intended to aid the recovery of these stocks generally fall into one of four categories, known as "the 4-H's": habitat, harvest, hatchery, and hydrosystem. Habitat actions focus on access to, and improvement of, habitat suitable for rearing juvenile salmon and spawning by returning adults. Historically, many parts of the Columbia River watershed have been degraded by logging, mining, farming, and development. Although legitimate economic activities, they have often caused unintended negative consequences for salmon populations. Salmon habitat has been fragmented and degraded by water diversions, obstacles to habitat by structures such as culverts and dams, and loss of vegetation adjacent to rivers and in watersheds. The RPAs specify actions related to upriver habitat where salmon spawn and down-river estuary habitat where salmon transition to their ocean phase. Actions to improve habitat include increasing stream flows, reducing water temperature, removing barriers to habitat, and increasing pools, spawning gravels, and side channel habitats. Other habitat actions include efforts to remove the salmon's predators, including California sea lions. Sea lions generally prey on the salmon congregating at the fish passage facilities, although it is suspected that they also consume salmon in other parts of the Lower Columbia River. In 2015, the Corps' monitoring program estimated that sea lions at the Bonneville Dam consumed 10,859 salmonids between January 1 and May 31, 2015, which accounts for 4.3% of the adult salmonid passage. To reduce predation on upstream migrating adult salmon, NMFS authorized Washington, Idaho, and Oregon to lethally take (i.e., kill) California sea lions that gather seasonally below Bonneville Dam. Individuals and animal rights groups challenged the take authorization in multiple lawsuits, but NMFS's latest authorization from 2012 survived the most recent court challenge, which has led to ongoing efforts to capture and euthanize California sea lions. Other predators include the pikeminnow, which feed on juvenile salmon and steelhead. BPA sponsors a program that pays for each pikeminnow caught in the Columbia River. For 2016, there is a reward of $5 to $8 per pikeminnow of at least 9 inches and a $500 reward per tagged fish. According to BPA, since the program started, over 4.2 million pikeminnow have been caught, reducing their predation on juvenile salmonids by 40%. Historically, salmon harvest was one of the main factors that contributed to the decline of Columbia Basin salmonid populations. Commercial and recreational fisheries in the Columbia River are co-managed by the states of Washington, Oregon, and Idaho, four treaty tribes, and other tribes that traditionally fished these waters. All fisheries are subject to review by NMFS for compliance with the ESA. Generally, managers have attempted to minimize the harvest of wild fish, especially listed populations, through a variety of actions. Harvest actions focus on limiting harvest or harm to listed species by requiring selective fishing gear or timing harvest periods to focus fishing on hatchery stocks. In mark-selective fisheries, the adipose fins are clipped on hatchery juveniles so fishermen can differentiate returning hatchery fish from wild adults. Hatchery efforts are intended to increase the number of fish through artificial propagation. Some assert that hatchery production reduces predator and harvest pressures on wild fish, while others are concerned that hatchery fish compete with wild salmon and steelhead for food and habitat. Hatcheries also may alter the genetic diversity of specific stocks. According to the Hatchery Scientific Review Group, a congressionally funded scientific review panel, hatchery management alone will not lead to the recovery of the endangered salmon and steelhead in the Pacific Northwest, but must be done as part of a broader strategy that incorporates actions affecting habitat, harvest rates, water allocation, and other components of the human environment. According to the NMFS Hatchery Listing Policy, under certain circumstances hatchery fish may be considered when estimating the populations of fish for listing determinations (i.e., when deciding whether an ESU might be threatened or endangered). Finally, hydrosystem actions that promote species recovery have concentrated on improving the survival of juvenile and adult salmon and steelhead as they migrate past dams and through reservoirs.