Healthy estuaries support resilient salmon populations

An estuary is a coastal body of water where freshwater rivers meet the open sea. Estuaries provide an important point of physiological transition for salmon and steelhead as they move from freshwater habitat to life in saltwater. Healthy, functioning estuaries provide productive feeding areas for young salmon and refuge from predators as they make this transition. Some Chinook salmon in the Columbia River estuary, for instance, spend days and even weeks in the same estuarine wetland channel as they undergo physiological changes.

Throughout the Pacific Northwest, estuarine habitat has been degraded or lost because of development activities and alterations to natural flows. In the Columbia River estuary, for example, nearly two-thirds of estuarine wetlands have been lost over the last century. The loss of this habitat has important implications for salmon. With reduced and degraded habitat, foraging success is limited, growth impeded, and survival reduced. Understanding the scientific relationship between estuarine habitat and healthy salmon populations is critical for conservation and protection purposes. As we work to prioritize restoration efforts, we must understand the ways in which salmon use the estuary and how they may benefit from targeted restoration actions.

Restoration activities are underway in several estuaries in the Pacific Northwest. In the Columbia River estuary, for example, the Columbia Land Trust, with support from the Bonneville Power Administration and the U.S. Army Corps of Engineers, recently purchased tidal floodplain habitat and will restore hundreds of acres of historical wetlands. Known as the Columbia Stock Ranch, the site encompasses a reach where much of the historical habitat is no longer accessible to salmon. An independent panel of biologists identified the parcel as an especially valuable swath of historical tidal wetlands that if restored would boost survival of young salmon as they transition to saltwater. By re-connecting historical channels, 545 acres will be restored and provide salmon with access to important rearing and foraging habitat. This restoration effort is promising, as it is located in an estuary reach with highly diverse salmon populations, including Lower Columbia River spring/fall Chinook, Lower Columbia River coho, Willamette River spring Chinook, Upper Columbia River summer/fall Chinook, and Snake River fall Chinook.

Insuring the integrity of our region’s estuaries is critical if we are to restore Pacific salmon and steelhead. Science will continue to shape the way in which we manage our estuaries to protect salmon, and it will continue to demonstrate where habitat reaches, if restored, will yield valuable biological benefits to fish.

Photograph: Estuary photo courtesy Dan Bottom, NOAA Northwest Fisheries Science Center