Salmon are anadromous fish, which means they are born in freshwater streams, spend their adult lives in the ocean, and return to freshwater streams to lay their eggs. Even more remarkable is the fact that many salmon return to the same stream in which they were born. Before juvenile salmon head out to sea, the fish spend time in estuaries to adjust to changing water conditions. An estuary is where freshwater mixes with salt water.
The Nisqually River supports several different populations of salmon, including the threatened Chinook and steelhead trout. Chinook salmon are the most estuary-dependent salmon species, and can serve as an indicator of the health of an estuarine habitat (Magnusson, A., and R. Holborn. 2003). The Nisqually Delta Restoration Project stands to benefit the Chinook greatly, because the amount of estuary habitat is expected to increase through time. Chinook salmon are listed as a threatened species under the Endangered Species Act; by completing this restoration, the Nisqually Tribe hopes to move one step closer towards the recovery of the Chinook salmon.
Habitat availability isn’t the only factor that is necessary for salmonid survival. The Nisqually Tribe and USGS have taken a three-pronged approach to monitoring salmonid response to restoration.
This monitoring approach was first outlined in Ecological assessment criteria for restoring andromous salmonid habitat in Pacific Northwest estuaries. (Simenstad and Cordell, 2000.)
Magnusson, A., and R Hilborn. 2003. Estuarine influence on survival rates of Coho (Oncorhynchus kisutch) and Chinook salmon (Oncorhynchus tshawytscha) released from hatcheries on the U.S. Pacific coast. Estuaries 26:1094-1103.
Simenstad, C.A., and J.R. Cordell. 2000. Ecological assessment criteria for restoring anadromous salmonid habitat in Pacific Northwest estuaries. Ecological Engineering 15:282-302.