Over the past two decades, U.S. federal agencies have pumped $3.3 billion into recovery efforts for endangered salmon in the Pacific Northwest — but there is no evidence that the money has paid off, according to a report issued yesterday by the U.S. General Accounting Office. The report is the government’s first comprehensive assessment of salmon recovery costs and outcomes, and it reaches a conclusion that has been suspected by critics for years: Federal agencies cannot prove that massive funding correlates to increased numbers of fish returning to the region to spawn. Part of the difficulty lies in accounting for natural variations in salmon populations and the effects of weather and ocean conditions. Sen. Mike Crapo (R-Idaho) said the report highlighted the need for greater accountability and reform of the Endangered Species Act.