Fish counters have seen record-breaking numbers of sockeye salmon pass through the fish ladders at McNary Dam in the past few weeks.
So far, more than 228,000 sockeye have passed through the dam - almost double the amount for the entire 2009 season and more the triple the amount of the 10-year-average.
Officials aren't able to attribute the spike in sockeye numbers to one single cause.
"It's hard to know precisely," said Brian Gorman of the Northwest division of the National Oceanic and Atmospheric Administration. "Clearly we have seen very good ocean conditions in recent years: not too many predators, lots of food and good water conditions."
Due to the large increase in the number of sockeye, the Oregon Department of Fish and Wildlife announced the opening of a recreational sockeye salmon season effective from June 26 through July 31.
Anglers fishing between the Astoria/Megler bridge over the Columbia and upstream to the Longview Bridge border are now allowed to keep up to two sockeye per day.
Between June 27-30 the sockeye passed through the locks at a rate upwards of 20,000 per day. Since then the rate has decline to about 8,000 per day.
"I think we're also seeing the effects of the efforts that have been made to improve river conditions and passage over the dams," said Gorman.
Fish counters have also observed that many of the sockeye appear to be larger than usual.
Other dams up and down the Columbia have reported similar spikes in the number of sockeye migrating upstream.
Fish counters have also recorded a larger than average spring run for Chinook salmon.
The majority of Chinook salmon migrate upstream August through October, but counters have already recorded about two thirds of the number of fish they would expect in a typical year.