Since 1976 Clatsop County, Oregon, has maintained a project along the Lower Columbia River, with salmon "net pens" first set up in Young Bay, and, as the project proved worthwhile, net pens were added in Blind Slough and near Tongue Point.
Fingerlings were raised and then released in the Columbia River as smolts.
According to Clatsop County's "Fisheries Project" information (2007), in 1977 the project released 50,000 coho. In 2004 the project released 2.4 million coho, 1.5 million spring chinook, and over half a million bright fall chinook smolts.
The chinook and coho fingerlings come from Oregon Department of Fish and Wildlife and U.S. Fish and Wildlife hatcheries, plus the Clatsop project receives eggs for incubation at its hatchery on the South Fork of the Klaskanine River.
The "net pens" themselves are floating fish pens secured to pilings along the shoreline.
A small-mesh net is suspended from a floating frame, made of high-density polyethylene pipe, that is secured to pilings. Each side of the pen is 20 feet long. The net hangs 10 feet deep. ...
The fish are raised in these pens various lengths of time, long enough for them to "smolt" a physiological change prior to entering salt water.
During their time in the net pens, the fish imprint to the scent of the bay, giving the the homing instinct to return to that location for harvest.
Before their release, the smolts from each group are marked so they can be identified when they return as adults and are harvested. Tiny coded-wire tags are inserted into the snout and the adipose fin is clipped. The fin is located on the topside of the fish near its tail. ..."
[Clatsop County, Oregon, website, 2007, "Fisheries Project"]
The Clatsop County project is just one of many net pen projects established along the Lower Columbia River, with other projects managed by the Oregon Department of Fish and Wildlife and the Washington Department of Fish and Wildlife, all with sponsorship by the Bonneville Power Administration (BPA). Net Pen sites are located up and down the Lower Columbia River, with locations at (as of 2007) Blind Slough, Youngs Bay, Tongue Point, Deep River (12 pens were installed in 1999 with 16 additional pens being requested in 2006), and Steamboat Slough near Skamokawa.