From Jan Newton, Allad Devol and Wendi Ruef, University of Washington:
A fish kill occurred in late August in Hood Canal, documented by observations from the Skokomish Tribe and by ORCA buoy oxygen measurements by the University of Washington. The fish kill was most severe on 29 August, but with stress and some mortality observed both before and after.
Seth Book and others from the Skokomish Tribe DNR observed thousands of dead fish and crab on Friday, which was covered by the media. On Saturday-Sunday, we anticipated even more fish kill, due to sustained southerly winds, but the lowest oxygen waters stayed deep, below ~10 m. Videos show the fish and crabs confined to a narrow surface layer, which maintained sufficient oxygen.
A couple things to clarify from the media reports:
- Worst year? The low oxygen levels in southern Hood Canal were the most extreme we have measured, even worse than in 2006 and 2010. However, the fish kill events in 2003, 2006 and 2010 appear to have been worse than this year, at least so far.
- Blob effect? The effect of the blob (warmer than typical NE Pacific ocean waters) was last fall, when the ocean waters entering Puget Sound were warmer (less dense) and did not flush the southern reach of Hood Canal. The year 2015 started with hypoxic waters in southern Hood Canal. The blob, still offshore now, is not affecting current conditions. Strong coastal upwelling during June is what is flushing Hood Canal now. This seasonal intrusion started about a month earlier than normal, which is lucky because oxygen conditions would have worsened until the flushing started.
Oxygen conditions in Hood Canal appear to be improving as flushing continues. Conditions today at Hoodsport show the entire water column is above hypoxic levels; at Twanoh there is severe hypoxia (less than 1 mg/L) at 10 m depth, but the deepest waters now have oxygen concentrations above this.
Visit ORCA and NANOOS for more information on hypoxia in Washington waters.
