Atlantic Salmon, Net Pens and Risks to Native Salmon


Sara Thompson, KP News

In August, an estimated 140,000 farmed Atlantic salmon escaped into Puget Sound when their net pen collapsed near Cypress Island in the San Juan Islands. Exactly what the risks will be to native salmon are not clear, but the incident has increased public awareness and scrutiny of the salmon farming industry.

Salmon farms have operated in Puget Sound for 35 years. There are currently eight net pens in Washington in four locations: near Cypress Island, near Bainbridge Island, at the mouth of the Skagit River and in Port Angeles Harbor near the mouth of the Elwha River. One company, Canada-based Cooke Aquaculture, purchased all the farms in Washington from Icicle, a Washington state company, in 2016.

At least 10 million pounds of salmon are raised annually in Washington, the only state on the West Coast that has commercial salmon farms; 100 million pounds are raised in British Columbia. The United States is a net importer of farmed salmon.

Opponents of salmon farming worry that escaped salmon might threaten native species by settling into habitat, competing for food or even preying on young chinook as they feed along the shoreline. Other concerns are pollution at the fish pen sites and the introduction of infections such as viruses or sea lice.

At the time of the net pen failure, the Lummi Nation declared a state of emergency and Kurt Beardslee, the director of Wild Fish Conservancy Northwest, called the escape an “environmental nightmare.”

According to evidence cited on the websites for the Washington State Department of Fish and Wildlife and the Department of Ecology, the risk of the escaped salmon successfully competing with the native species is low. The SeaDoc Society, a nonprofit organization founded in 1999 whose mission is to “protect the health of marine wildlife and their ecosystems through science and education,” published an article that concurred with this assessment. (

Kathleen Peters, a fish biologist from the peninsulas region, feels that the facts warrant reassurance. “I feel the risks are minimal,” she said. “The escaped fish have no clue how to be wild. There has been some successful spawning documented in rivers but no resulting colonization.”

As recently as the 1980s, WDFW actively tried to introduce Atlantic salmon to Puget Sound waters. None of the smolts released returned as adults. Between 1987 and 1996, over 250,000 salmon escaped from pens in Washington and British Columbia. Nearly 11,000 Atlantic salmon were caught as far away as Alaska in that time span, indicating that they could survive and swim long distances. Studies of streams in British Columbia have shown colonization by Atlantic salmon in small numbers but they are not considered “established.” There are no known self-sustaining, wild populations of Atlantic salmon in Washington waters.

The risk of Atlantic salmon eating young native fish or competing for food is low, according to WDFW; all of the escaped Cypress Island fish that were caught and examined had empty stomachs.

Sea lice and viral infections are potential problems but have not been significant to date. Peters said, “When I was a fish pathologist, I found a virus that had never been found in North America. We suspected and tested the Atlantics in net pens, but they were not the source. Eventually, we found the virus in marine fish species.”

Sea lice naturally exist in the wild populations of native Pacific salmon. According to Ecology, aquaculture practices disrupt the sea lice life cycle and commercial net pens in Washington do not have significant sea lice problems.

The Monterey Bay Aquarium's Seafood Watch program upgraded its rating of British Columbia farmed Atlantic salmon from “avoid” to "good alternative” in September. The Seafood Watch report said: “There is currently insufficient evidence to conclude that population-level impacts to wild salmon are occurring due to pathogen and/or parasite transfer from salmon farms.”

But the report also added: “Overall, there is clearly a pathogen and parasite concern with regard to the location of salmon farms along migration routes of wild salmon.”

The most recent recommendations from the state regarding commercial salmon farms date back more than 20 years. In the spring of 2016, Ecology took the lead in a project to update those recommendations in Puget Sound, Willapa Bay and Grays Harbor. The departments of agriculture and fish and wildlife are partners in the project; technical assistance is provided by the National Centers for Coastal Ocean Science. Staff of the Port Gamble S’Klallam Tribe and Northwest Indian Fisheries Commission are advising the effort. A final report is due in the fall of 2019, including a geospatial analysis tool to help with evaluation of any new permits.

Curt Hart, communications manager for Ecology, said the impetus for the project came from local governments that issue permits for aquaculture and need updated information for shoreline management programs. Pierce County prohibits net pens south and west of the Narrows Bridge.


A Quick Guide to Salmon Farming

Eggs are hatched and young salmon are raised in closed ponds, much as they are in state hatcheries.

After about a year, the young salmonids are transferred to net pens, where they are fed daily with pellets. Sixteen to 20 months later, they are harvested. They are pumped into a ship and taken alive to a processing facility.

Net pens are formed by joining cages together. (At Cypress Island, there are three net pens, each consisting of eight to 12 cages. The cages are 15 meters deep, 24 meters wide and 24 meters long.) Cages are held under water by weighting systems and moored with anchors. Structures are expected to last for about 15 years.

The pens are protected from predators such as seals by heavy-gauged nylon netting around the pens.

The site for a pen must have water that is of appropriate depth and has current and tide motion that will provide good oxygenation but is not too rough on equipment. It can’t interfere with navigation or current shoreline uses. [/box]