Prior to the incident, Washington was the only US state on the Pacific coast where Atlantic salmon was farmed. Atlantic salmon are favored by salmon farmers, since their domestication process is much farther along; farmed Atlantic salmon have been selected for faster growth, higher tolerance to disease, and greater docility. The net pen was managed by Cooke Aquaculture, a Canadian company based in
New Brunswick and one of the largest
aquaculture companies in the world. It took over the Cypress Island aquafarms in 2016. The pen that was breached was a 10-cage salmon pen that contained 305,000 fish, and had been placed in 2001. It was anchored in
Deepwater Bay, southeast of Cypress Island and to the west of Bellingham Channel (which separates Cypress Island from
Guemes Island). The pen was submerged from to , and was approximately wide by long. The August 2017 pen break was preceded by an incident a month earlier with the same pen; on July 24 and 25 its mooring failed, was restored, failed again, and was restored a second time. This incident occurred during the strongest tidal currents of the summer of 2017. The salmon pens had been stocked with 369,312 smolts in May 2016, and had been scheduled to be harvested starting September 2017. At the time of the incident, the
biomass held by the salmon pen was estimated to be around . ==Incident==