The decline of salmon runs in the Northwest is hurting a number of other fauna and flora, including insects, bears, plants, and trees that depend on rotting salmon carcasses as a source of nutrients from the ocean, according to a study published in the latest issue of the journal Fisheries. Just 5 percent to 7 percent of the historical biomass of salmon are returning to their native watersheds, the study authors estimate, creating a dramatic shortage of nutrients. “We have essentially starved our freshwater systems,” said Bob Bilby, a fisheries scientist with the National Marine Fisheries Service in Seattle. For the past two years, volunteers in Oregon and Washington have been tossing salmon carcasses from hatcheries along rivers to help spread nutrients, but they can’t toss enough to replicate the natural processes of the past.