"There is really great real-time data available to inform us about conditions in the ocean, and that information is key for predicting how salmon will fare as they enter the ocean at any given time," said McMichael. "Perhaps we can take advantage of that data to determine optimal conditions for releasing hatchery-raised salmon, for instance, and when to hold back."
The study provides a snapshot of salmon behavior at a crucial time, after a migration from their freshwater birthplaces to the ocean, a journey often hundreds of miles long. Depending on the species and their age, the fish generally travel anywhere from 20 to 60 miles a day, carried by the current as they navigate much of the journey backwards tail first.
Previous studies had indicated that as they exit the Columbia River, most salmon head north up the coast of Washington state, essentially turning right as they exited the Columbia. But the new study showed that while many salmon, especially the youngest, head north, many others head straight out to the ocean, and many others head south. This indicates that the number of salmon safely reaching the ocean may have been undercounted in previous studies, since researchers focused their monitoring efforts toward the north, McMichael said.
The study also showed that the length of time that fish stay in the transition zone between the mouth of the river and the ocean varies greatly as well. Steelhead are more likely to bolt straight into the ocean within a few hours, while the youngest Chinook salmon, less than a year old, are likely to go back and forth a bit for a few days before committing to ocean life.
A surprising finding was that the biggest, strongest, fastest fish in the study steelhead were also most likely to
|Contact: Tom Rickey|
DOE/Pacific Northwest National Laboratory