Salmon migration and survival
I studied salmon ecology for two years as a fisheries biologist for the Northwest Fisheries Science Center in Seattle. My research focused on salmon survival as they migrated past the dams in the Columbia River basin.
Salmon have an extraordinary lifestyle. They start their lives in river tributaries and migrate hundreds or even thousands of miles to reach the ocean. Then after a few years of eating and growing, they undertake the journey of their youth in reverse, swimming upstream to spawn in the tributaries that birthed them. Most species in the Columbia River basin (ie. Sockeye and Chinook) die once they spawn.
Migrating salmon swim thousands of mile to spawn in streams like this one in Idaho.
Migration is fraught with peril. In the past, adult salmon swimming up the Columbia River Basin had to scale huge waterfalls (like Celilo falls) and avoid getting chomped by bears. Today, the greatest threat to their migration journey is the systematic modification of their habitat through dams. Over a dozen dams have been built along the Columbia River and these have changed the salmon migration corridor from free-flowing run of the rive to a series of stratified water basins. Besides the challenge of the physical barriers posed by dams, salmon also need to contend with the increased temperatures of stratified basins — temperatures that are only likely to increase with global climate change.
I’m catching small invertebrates that feed juvenile salmon, in an Idaho stream.
My research at the Northwest Fisheries Science Center consisted of modeling the survival and migration timing of salmon as they migrated past the dams of the Columbia River on their return journey to their natal tributaries. I used data from Passive Integrated Transponder tag, or PIT-tag, data which had been collected for over ten years. Researchers inserted PIT-tags (small cylinders a few millimeters long) into juvenile salmon and when salmon pass receiver stations, the PIT tags are detected and we can access oodles of information about that particular fish: when and where it was tagged, what species it is, whether it was a wild or hatchery fish. There are receivers in each fish ladder, so by using information collected at each dam, we can examine the migrational success of salmon as they swim up the Columbia River.
These juvenile salmon are waiting to be tagged. They will provide important data to researchers throughout their lives.
This research will help managers better understand and predict the cumulative impact of dams and climate change on these protected salmon species. It will also help them decide on mitigation possibilities, like hatcheries, transporting fish, and modifying flow.