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Pacific Coastal & Marine Science Center

Coastal and Marine Earthquake Studies

Western Coastal and Marine Earthquake Studies.


SHIPS: Seismic Hazards Investigation in Puget Sound

Map of Lake Washington Fish Kill

Map of Lake Washington Fish Kill

Dead fish were found while airguns were being used in Lake Washington. The survey ship never went south of the Highway 520 bridge. Even so, some dead fish were sighted in a southern group near Mercer Island. Significantly, this sighting occured 1/2 hour before the airguns were first used north of Sand Point. The wind blew from the south-southwest all day, so there was insufficient time for dead fish from Sand Point to have drifted 6 miles upwind to Mercer Island. It is clear that something other than airguns killed the fish in this southern group. A single fish recovered from this group awaits an autopsy.

Dead fish were also found north of the 520 bridge, along the southern part of the ship track. These fish were observed ahead of and upwind of the ship. Biologists working on the ship's foredeck said the fish were bloated and stinking and had been dead for a long time. The reason why fish in this northern group died is unknown because no fish were recovered.

The survey party immediately instituted procedures to mitigate harm to fish. At our request an investigation of the fish deaths was conducted The preliminary results of the investigation are inconclusive. During the survey we repeatedly sent a small boat to inspect our wake but found no dead fish. Frequently, small boats came from shore to inspect our wake but never reported dead fish.

This fish kill was the subject for front page headlines and much media attention. Several hundred dead fish were first reported; later reports exaggerated this to a miles-long slick of dead fish and finally to millions of dead fish. However, after firing the airguns along the track line shown in red in the figure above, we recovered the airgun array and retraced much of our path to the north, toward Kenmore, where we had earlier discharged the airguns. Thirteen news reporters and six biologists had heard reports of dead fish, and despite their heightened awareness, they sighted no dead fish along our retraced path toward Kenmore. This is the area where the "miles long slick" of dead fish was supposed to have been discovered.

Intensive media coverage continued until it became clear that the fish kill could not be attributed to airgun operations.

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