The Hood Canal, which is actually a 600 foot deep fjord on the Puget Sound, is a dive Mecca for thousands of divers each year from Western Washington and Oregon. According to the “Hood Canal Dissolved Oxygen Program” The Hood Canal has a recurring problem with dissolved oxygen levels because a shallow ‘sill’ at the entrance creates a condition in the canal that doesn’t allow the water to flow or exchange very easily with the changing tides and seasons. The entrance to the canal is relatively shallow, about 150’ but the depth below the entrance the canal quickly drop off to 500 and 600’. The ‘sill’ tends to retain the water (reduces the exchange) in the canal and estimates of complete water exchange rates are in the magnitude of years.
University of Washington oceanographer Jan Newton reported situation is worsening and that the conditions are similar to 2006 when thousands of fish died and washed on beaches. The tipping point for a fish kill can be when the strong south winds create surface currents that cause the deeper low-oxygen waters to come to the surface.
Although we do not know the exact connection, we have seen clouds of mysids and plankton blooms in the 25-45 fsw area for months.