Associated Press

SEATTLE — State investigators are examining nets heavily covered with mussels and other sea life as a cause in the collapse of net pens at a salmon farm last summer that released thousands of non-native fish into the Salish Sea.

Photos obtained by The Seattle Times show portions of nets at Cooke Aquaculture’s operation off Cypress Island so covered with mussel and other growth that the net was no longer visible. The photos show heaps of mussels on the dock when the nets were lifted with a crane to be disposed.

Cooke is required under terms of its state lease to keep it farms in a clean and safe condition.

Nets that accumulate too many organisms or material such as mussels, kelp or algae can cause drag and change the way the nets behave underwater in tidal currents. It can also block mesh openings and impede flow of water through a net-pen.

Early on state investigators focused on the issue of net fouling as chunks of the collapsed fish farm were hauled up and disposed of after the August net-pen collapse. Investigators preserved pieces of net in mussels for evidence, The Times reported.

“It’s possible these animals played a significant role in the failure of net pen #2,” Dennis Clark, assistant division manager for the state Department of Natural Resources wrote investigators on Sept. 10, reviewing photos of heavy mussel growth on the nets.

Cooke’s vice president of communication, Joel Richardson, declined to comment on the nets or maintenance issues at Cypress Island.

“We are cooperating fully with the regulatory agencies as their investigation is underway,” Richardson wrote in an email to The Times. “As such, it would not be appropriate for me to provide comments.”

Employees confirmed to investigators that two of three machines used to clean nets were being repaired, reducing the ability to keep up with the net fouling issue, according to notes written by state investigators from interviews with employees and which were obtained by The Times.

Workers continued to clean the nets by using a vacuum device to suck kelp off, Innes Weir, Cooke’s general manager in Washington, told investigators. Cooke brought in equipment from its other farms, and got the nets 80 percent clean. “Staff are aware of the problems caused by fouling,” Weir told investigators.

Investigators from multiple state agencies are expected to report their findings on the August farmed salmon escape Tuesday.

Several bills introduced in the Legislature would phase out or terminate Cooke’s aquaculture operation in the state.

Washington is the only state on the U.S. West Coast with open-water Atlantic salmon net pens in its public waters.

Leaders from 21 Washington tribes sent a letter to state lawmakers this month requesting that open-water Atlantic salmon net-pen farming be shut down as soon as possible to protect native salmon.

Cooke employees and lobbyists have testified in Olympia to defend the aquaculture operations and the jobs they support. Cooke has invested more than $70 million in the farms, and plans to upgrade and expand its operations, Cooke executives previously told state lawmakers.

Cooke owns and operates commercial salmon farms at eight locations in Washington state that it acquired in 2016. Many of the operations have been around for decades. It is the nation’s largest producer of farmed salmon.