According to Bosse, barging disrupts that cycle by completing the last 465-mile journey from Lower Granite Dam to the Columbia River Estuary, where freshwater and saltwater mix, in a day and a half instead of a couple of weeks. That's the equivalent of taking a human at sea level and transporting him to the top of Everest and expecting him to adapt right away. When the fish are released into the estuary, they tend to gravitate to a thin layer of freshwater at the surface, Bosse noted. This puts the fish at great risk of being eaten by a number of predators. Conservationists also claim that disease is rampant in barges.
Conservationists say all the factors add up.
Less than 2 percent of the smolts return to the rivers as adult salmon. In order to restore the populations, biologists say they need a return of between 4 and 6 percent. Increased exposure to disease and predation means a lot of delayed mortality. All Rights Reserved. Terms under which this service is provided to you.