Just how much of an obstacle course can a salmon run to its spawning grounds? With the building of increasing numbers of dams on the Columbia and Snake rivers, the Chinook apparently have lost their lust for the climb. The opening of the John Day Dam in April brought the number of major barriers that the salmon must hurdle to six. They now must climb more than a mile of fish ladders to reach the areas where they reproduce.
Since the completion of the new dam, the Oregon Fish Commission has kept a close watch on the number of Chinook successfully making the climb. Of the 75,000 fish counted passing the first dam on the river, slightly more than half have made it over the John Day, which is located about 65 miles upstream, and only 30% have reached the major spawning grounds in the Snake River. The commission estimates that half the summer run will not be able to reproduce.
The new dam has not created a new problem, but it is severely aggravating the one that already existed. Besides adding a hurdle, it is increasing the nitrogen in the river, causing the death of hundreds offish. The water going over the dam absorbs a large amount of nitrogen under the force of impact with the water below. If the reaction to the nitrogen is acute enough, gas bubbles form in the Chinook's blood and it is subject to something like the bends experienced by deep-sea divers.
Researchers are now talking about transporting the Chinook around dams to avoid the spillways. That seems like an awkward and temporary solution. They might think about digging a river for the fish parallel to the Columbia.