Speculation has been flying this week that a 2008 volcanic eruption on an Alaskan island was responsible for this year's glut of salmon in rivers in British Columbia, Canada. If confirmed, the idea will improve biologist's understanding of the notoriously unpredictable size of salmon runs, and add fuel to the controversial idea of intentionally seeding the ocean with iron to boost diminishing fish stocks. But some researchers contacted by Nature warn that the theory is "far fetched".