Fish-kill risk in Hood Canal

HOOD CANAL — Severely low oxygen levels in southern Hood Canal have created conditions that could lead to a massive fish kill, experts say.

The trigger would be strong winds out of the south, which would bring low-oxygen waters to the surface, potentially killing thousands of fish in a short time, said Jan Newton, a University of Washington oceanographer. Newton observed similar conditions in September 2006, when thousands of dead fish washed up on shore.

"I'm not predicting a fish kill," Newton stressed, "but things are setting up with the right ingredients."

Based on 40 to 50 years of data, the oxygen content of Hood Canal south of Dabob Bay reached a record low at the end of August. A monitoring buoy at Hoodsport, Mason County, also shows a record-low level for this time of year.

The genesis of this year's problem is a deep layer of low-oxygen water left over from last winter. For some reason, that water uncharacteristically failed to flush out.

Typically in the fall, a deep layer of dense, oxygenated water pushes in from the Pacific Ocean. That layer tends to come in under the less-dense water in Hood Canal, pushing low-oxygen waters upward. At the same time, low-oxygen waters from Belfair to Twanoh advance toward Hoodsport as rains wash into lower Hood Canal.

When strong south winds hit the Big Bend area near Hoodsport, the surface layers of Hood Canal are blown to the north, forcing low-oxygen waters up toward the surface. Fish will swim upward, trying to find oxygenated water, but they may have no place to go.

Such conditions do not always lead to a fish kill. In 2004 the deck was stacked with low-oxygen water, yet the lack of a strong south wind may have avoided a fish kill.

"What is clearly evident," Newton wrote Tuesday in a condition report, "is that 2010 is a particularly low-oxygen year, even compared to historical records. ... The summer 2010 oxygen values are the lowest or among the lowest seen in the records available for the months of June and July for years spanning 1952-1966 and 1998-2010, with the August 2010 data point the lowest on record."

People living along the shore are urged to watch for dead sea life or other unusual conditions. Anyone with such information may call the Spills Hotline, 800-424-8802.