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Net Pen Aquaculture

WFC Net Pen Aquaculture Campaign


fish farmPuget Sound contains commercial salmonid net-pen aquaculture facilities, including eight large facilities that grow marketable-sized Atlantic salmon (exotic to Puget Sound). Net-pen fish harbor parasites and disease-causing organisms that can infect wild fish. In 2012, at the exact time wild salmon juveniles were migrating through Puget Sound, three Atlantic salmon net pens suffered from an outbreak of Infectious Hematopoietic Necrosis virus (IHNV). While thousands of net-pen fish died, the permits issued to the facilities do not require wild fish populations to be monitored for virus exposure. Both state and federal agencies promote aquaculture as a “sustainable” use of public waters, but the public does not have a clear sense of the risks.


Research in northern Europe, Chile, and Canada indicates that net-pen aquaculture poses serious risks to wild fish, but in the Puget Sound region, the ISAv imagerisk is rarely acknowledged in recovery-planning efforts. Because native juvenile salmon must pass through Puget Sound as they emigrate to the ocean, net pens expose the smolts to pathogens and parasites at the life stage when they are most vulnerable.

Aquatic pathogens can regulate fish populations via host mortality and reduced fecundity, particularly when pathogen transfer rates are high, as among farmed/captive fish populations. Parasitized fish are more vulnerable to predation due to behavioral changes or decreased fitness.

Recent detections of particular piscine viruses in farmed Atlantic salmon from the Pacific Northwest (including B.C. and Puget Sound) highlight the risk of pathogen transfer to wild salmon via the open water net pens currently used in salmon aquaculture. Fish with poor nutrition or increased stress (as in aquaculture settings) are more vulnerable to disease. Pathogens from net pen salmon aquaculture facilities may impact native salmon populations in three ways 1) introduction of exotic pathogens from non-native fish; 2) amplification of pathogens due to the high density rearing conditions found in aquaculture facilities; and 3) selection for increased pathogenicity as the conditions found in net pens are conducive to the emergence of highly pathogenic strains.

Sea lice 2While sea lice are a natural epizootic parasite of wild adult salmon, they are rare on wild juvenile migrants. Recent large-scale blooms of sea lice, however, are correlated with establishment of adult salmon farms. Increased lice loading is fatal or detrimental to wild juvenile fish, and research conducted by WFC indicates an increase in the infection rate of wild juveniles observed in the proximity of Atlantic salmon net pens. Further research is needed to determine if population-level effects are occurring.

WFC is in the process of conducting piscine virus surveillance in Puget Sound.

Additional Information

Here are some of the papers, reports, articles and videos we feel are important to gain a better understanding of salmon aquaculture and it's potential impacts to Puget Sound.

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