By Marcy Stamper

Although the hundreds of thousands of Atlantic salmon that escaped when a commercial net pen ruptured last August were far from the mouth of the Columbia River — the portal to headwaters in the Methow Valley — the importance of salmon recovery to the local ecosystem and economy alarmed fish biologists here, along with their colleagues around the state.

An investigation completed last month by three Washington departments, Natural Resources, Ecology, and Fish and Wildlife (WDFW), found that 110 tons of mussels and plants had accumulated on the nets — an average of 11 tons per net — causing the nets to fail.

The net pen, near Anacortes, was operated by Cooke Aquaculture and contained 305,000 Atlantic salmon. The investigation said 243,000 to 263,000 of the fish escaped.

The investigation found that tidal currents had pushed against the mass of organisms on the nets, overwhelming the mooring system and crushing the pen. Extensive corrosion of the structure also contributed to the collapse, they found.

Photographs in the investigation show nets completely covered in mussels and plants. “Videos document a ‘rain’ of mussels falling from the nets. Loose mussels were swept in piles about three feet high on the deck of the crane barge,” according to the investigation.

Monitoring throughout the winter and of next fall’s salmon runs will be critical for scientists to learn if any escaped Atlantic salmon remain in Washington’s waters and if they are reproducing, according to the investigation.

The agencies also identified shortcomings in Cooke’s engineering practices that had likely contributed to the failure. “Cooke’s disregard caused this disaster and recklessly put our state’s aquatic ecosystem at risk,” said Commissioner of Public Lands Hilary Franz.

In addition to blaming Cooke for the rupture of the structure, WDFW criticized the company for under-reporting the number of fish that escaped and over-reporting the number that had been recovered.

Although Cooke reported extracting 145,000 fish from the collapsed net pen, the investigation concluded that the company could only have extracted between 42,000 and 62,000 salmon. Previous estimates based on Cooke’s reports had put the number of escaped fish at 160,000.

Commercial and recreational anglers were encouraged to catch as many of the fish as possible, which were considered safe to eat. The investigation found that only 57,000 had been caught, meaning that between 186,000 and 206,000 Atlantic salmon are still unaccounted for.

After the net pen ruptured, the fish were congregating in the shallows in the sound near the pens, Bruce Botka, a WDFW spokesperson, said last summer. Some swam north toward the Strait of Georgia, and some were caught in the Puget Sound, but the fish did not appear to be heading further south toward the mouth of the Columbia, he said. A limited number were caught in the Skykomish and Skagit rivers, according to the investigation.

Because the fish spend their lifetime in nets, they don’t have the genetic material that tells them to go to a place to spawn, said Botka. “Atlantic salmon stocks employed by Cooke are highly domesticated with over eight generations (32 years) in captivity and dependent on artificial diets.” according to the investigation. Most recovered fish appeared not to have eaten since their escape.

A WDFW study of spills of Atlantic salmon in the 1990s found that escaped fish were not colonizing local watersheds and had not significantly affected native fish, although it did find some evidence of naturally produced Atlantic salmon in streams in British Columbia, indicating that escaped Atlantic salmon are capable of successfully producing offspring in the wild.

Cooke Aquaculture raised Atlantic salmon at eight locations in the Puget Sound under leases with the state. In October, just two months after the rupture, the company was cited for failure to repair nets and infrastructure near Bainbridge Island. In December, DNR terminated Cooke’s lease of state aquatic lands in Port Angeles, citing the company’s failure to maintain the facility in a safe condition.

Franz is expected to issue a decision about the ruptured facility near Anacortes in the near future. Ecology intends to take enforcement action against Cooke Aquaculture for violations of state water-quality laws.