Open the loodgates
Flood prevention on the Fraser could be hurting salmon, study inds
As researchers continue to study why salmon populations on the Fraser River have fallen to historic lows, two new studies show that floodgates on the river could be reducing habitat for fish — and there is little oversight when it comes to checking the ecological impact of that infrastructure.
“Past research in our lab had found that these floodgates were associated with low oxygen quantity in the creeks flowing into the Fraser through the floodgates,” said Rebecca Seifert, the lead author of a study by Simon Fraser University.
“They were seeing a dead zone where it was hard for sensitive fish like trout and salmon to survive.”
The floodgates, many of which were installed decades ago, reduce the flow of water, meaning more algae grows around the gates and lowers the oxygen level.
Researchers have also found more invasive species and fewer native species near floodgates — and there are over 300 gates between Delta and Hope.
When the gates are closed, juvenile salmon can’t get out of the creeks where they were born to pass down the Fraser River and out to the open ocean, an important part of the salmon life cycle.
Seifert wanted to know just how often the floodgates were closed, so she installed timelapse cameras.
She found that many of the gates, which close when high water pressure pushes them closed, are shut almost all the time during the highwater spring season. That’s also when juvenile season are trying to migrate to the Fraser.
A bald eagle eats a chinook salmon along the Harrison River.