Ocean conditions and survival

Ocean survival of Lake Washington anadromous species varies greatly from year to year due to highly variable conditions in the marine environment. Salmon survival can be impacted by estuary conditions, food availability in Puget Sound and the ocean, predation, ocean conditions such as El Nino, La Nina, the Pacific Decadal Oscillation, and ocean upwelling.

The effects of these conditions can combine to make for extremely poor ocean survival. Sometimes poor survival can be due to conditions when adult salmon are returning, other times it can be the conditions that they experience when they migrate out into the ocean.

Because different species spend different amounts of time in the ocean, impacts during out migration may be seen in different years for different species of salmon.

Migration and return examples

  • Coho salmon migrating out of Lake Washington in the spring will return in the fall of the following year.
  • Chinook salmon leaving Lake Washington in the spring will return mostly in the fall three years later—some will return two years later, some four years later.

So, if there were more predators at the mouth of the Strait of Juan de Fuca during the spring and summer of 2006 than usual (possibly due to El Nino conditions), coho returning in 2007 and Chinook returning in 2009 would have lower marine survival rates.

The overall number of returning fish will also depend on how many adults spawned in the parent years and freshwater survival rates.