OLYMPIA - Fishing for smelt, rockfish and a number of other deepwater species remains closed in Hood Canal, where hundreds of fish have been found dead and dying during the past week.
Tests conducted by the state Department of Ecology and the Hood Canal Salmon Enhancement Group (HCSEG) indicate that the large-scale fish kill was caused by extremely low dissolved-oxygen levels the water, said Greg Bargmann, marine fish manager for the Washington Department of Fish and Wildlife (WDFW).
Area residents have reported seeing hundreds of shrimp, blennies and gunnels, along with dozens of rockfish, striped perch and other fish, dead on the beach. WDFW divers, dispatched to investigate, found those and other species - including flounder and a Pacific octopus - dead underwater.
WDFW, together with representatives from the Skokomish tribe and volunteers from the HCSEG, found that the fish kill extended from the Potlatch area to north of Hoodsport.
"Last week's fish kill confirms our fears about conditions in Hood Canal," Bargmann said. "Dissolved-oxygen levels have dropped to the point where they're lethal to a variety of species. The best thing people can do is observe the fishing closures, so we don't make things any worse for these distressed species."
Extremely low dissolved-oxygen levels, a chronic problem in Hood Canal, were detected in the 60-mile-long fjord through routine monitoring in early August. In mid-September, WDFW closed fisheries for deepwater species most likely to be affected by those conditions.
The ongoing closure includes all recreational and commercial fisheries for octopus, squid, rockfish, surf perch, herring, smelt, flatfish, hake and other forage fish and bottomfish. Fisheries for salmon and trout were not included in the emergency closure, because they are generally less vulnerable to the oxygen-depleted conditions, Bargmann said.
Since August, oxygen levels in southern Hood Canal have been low enough below the depth of 10 meters to cause death in some marine organisms, said Jan Newton, an oceanographer for the state Department of Ecology (Ecology). That condition, called hypoxia, can occur when oxygen levels in the water fall below two milligrams per liter.
To escape those conditions, some fish rise toward the surface, where oxygen levels tend to be higher, Newton said.
"But some of the latest readings show the low oxygen levels extend all the way to the surface," she said. "The fish and other marine organisms just can't escape it."
While low oxygen levels are not new to Hood Canal, both the duration of low-oxygen events and the area affected by them have been increasing in recent years, Newton said. The reasons for this growing problem are not fully understood, she said, but may include increased nutrient levels from pollution in runoff, changes in circulation patterns resulting from river management and changes in ocean conditions.
Since August, the HCSEG, with assistance from the University of Washington (UW) and Ecology, has been monitoring dissolved-oxygen levels on a weekly basis, supplementing monthly data compiled by Ecology. Those organizations, along with WDFW, the UW and area counties, tribes and other local groups, are working to understand the nature of the problem and to develop recommendations for corrective actions.
"The good news right now is that we haven't seen a new wave of mortalities in the past few days," Bargmann said. "But it's still hard to say whether we're through the worst of it."
For more information, visit http://www.prism.washington.edu/hcdop/index.html and click on "citizen monitoring" for the latest sampling results.