Sockeye salmon are heading back up the Columbia River this summer in numbers unseen since 1955, and nobody is sure why.

Some credit a federal court order releasing extra water over dams in 2006 and 2007 to ease the young salmons' passage to the sea, The Oregonian reported. Others cite improved ocean conditions.

But the returning numbers exceed any year since the last major dam was built on the Columbia or Snake rivers. Sockeye were close to being written off in parts of the Northwest's largest river system.

Fish counters have recorded the return of nearly 215,000 sockeye, or red, salmon through Tuesday.

The rest of this article can be viewed by clicking here.