There is no evidence Atlantic salmon successfully interbreed with Pacific salmon. In the last century, attempts were made to introduce Atlantic salmon into Washington and 33 other states without success. The last attempt occurred in Washington in 1981 by the state Department of Fish and Wildlife. There are no known self-sustaining wild Atlantic salmon populations in Washington waters. State and national fisheries experts say there is a low risk that Atlantic salmon could be established here.
Commercial marine Atlantic salmon net pens have temporary impacts on sediment quality and benthic life. Net pens must comply with numerous local, state, and federal requirements. Since 1991, all commercial net pens must comply with state and federal water quality standards under a National Pollutant Discharge Elimination System (water quality) permit. Once a net pen is moved or closed, it takes two to 12 months for the substrate to recover. Commercial operations also close their net pens after every harvest cycle to reduce environmental impacts.
Our studies in Puget Sound show net pens have not been a significant source of nitrogen. Ocean currents, the atmosphere, urban and agricultural lands, septic systems, and wastewater treatment plants all contribute more nitrogen than net pens.
Sea lice naturally exist in wild native Pacific salmon populations and other fish species. While sea lice can spread to net-pen fish, Washington's commercial net pens do not seem to have significant sea lice problems. In addition, industry leave their pens empty for a while after harvest which helps sediments below the net recover while the nets are removed and cleaned on shore. This also disrupts the life cycle of sea lice.
Each state’s approach differs. Alaska prohibits raising or farming Atlantic salmon. Oregon does not prohibit Atlantic salmon aquaculture while California has adopted a more complicated approach to finfish aquaculture in general and Atlantic salmon specifically.
With the largest marine finfish aquaculture in the United States, Washington's eight marine net pens produce about 17 million pounds of Atlantic salmon annually.