Photo of Kasatochi courtesy of the Daily Galaxy
According to an article in The Daily Galaxy on October 13, 2010, the eruption of Alaska's Kasatochi volcano in the Aleutian Islands in 2008 put out a swath of iron rich ash that fell on the ocean and floated.
This ash led to a huge bloom of ocean plankton, which fed on it. Plankton is a food eaten by salmon when at sea.
In November 2010, Randy Shore wrote in the Vancouver Sun that huge salmon returns up the Fraser River in British Columbia may be related to the unusual quantities of ocean plankton available as food. He cites scientists from UBC, the University of Victoria and Simon Fraser University who support this view.
Volcanic soil has long been known to be fertile; evidently it provides fish food too. Volcanic activity, the visible process of earth-making, is a mixed blessing. Along with trouble, it brings fertile soil and rich plant food to the surface of our planetary home.