In an article published in the US journal Science, federal biologists laid out the government’s position that breaching Snake river dams is not an effective solution to save the salmon. In July this year, the US Fisheries service recommended that the four dams operated by the US Army Corps of Engineers (Lower Granite, pictured, Ice Harbour, Lower Monumental and Little Goose) be left intact while other steps are taken to help salmon. These actions would focus on restoring the rivers and streams where salmon spawn and restoring the Columbia river estuary.

The new study is based on a mathematical model to analyse how improved survival at each stage of the salmon’s life cycle — just after hatching in streams, swimming past the dams, lingering in the estuary and growing to adulthood in the open ocean — would translate into greater overall health of salmon populations. The biologists found that greater survival in the early life stages and in the estuary has the most dramatic effect on population growth. Under some of the study’s assumptions, the improvements in survival from removing dams would be too little to save Snake river spring/summer chinook.