Biofouling could have caused Cooke's cage collapse
Tuesday, January 30, 2018, 00:40 (GMT + 9)
Researchers from the state of Washington are examining whether the presence of large quantities of mussels and other marine organisms in the nets may have been the cause of the collapse of a Cooke Aquaculture salmon cage, which caused the escape of thousands of fish in the Salish sea.
Cooke had programmed to harvest in September about 3 million pounds of Atlantic salmon, which represent around 305,000 fish, in its farm located off Cypress Island.
Cooke is required, under terms of its state lease, to keep its 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.
Cooke´s employees confirmed that two of three machines used to clean the nets were out of service and being repaired, reducing the ability to keep up with biofouling, a problem that intensifies in the summer.
“Keeping the nets clean is important because fouling changes the way they behave underwater in tidal currents. A net creates drag in the water as current is impeded by its webbing. Any sea life or other material that covers and clogs the webbing adds to that drag,” explains Parker MacCready, professor of oceanography at the University of Washington.
Last September 10, after assessing the same photos of heavy mussel growth on the nets, Dennis Clark, assistant division manager for the Washington Department of Natural Resources, wrote in a statement, “It’s possible these animals played a significant role in the failure of net pen #2.”
Cooke’s vice president of communication, Joel Richardson told he Seattle Times that they are “cooperating fully” with the regulatory agencies as their investigation is underway.
While investigators from several state agencies are expected to report their findings on the spill, the state Legislature is considering to send several bills to phase out, or immediately terminate, Cooke’s operations in Washington.
Leaders from 21 Washington tribes also sent a letter to every state lawmaker requesting that Atlantic salmon open-water net-pen farming be closed in Washington as soon as possible to protect native salmon in Puget Sound.
Cooke owns and operates commercial salmon farms at eight locations in Washington state that it acquired in 2016, and it is the nation’s largest producer of farmed salmon.