British Columbia

Fraser River salmon impacted by floodgates, according to new SFU study

Replacing and retrofitting old and malfunctioning floodgates could be a 'game changer' for salmon survival

Karin Larsen - CBC News

October 05, 2017

A new study out of SFU has found floodgates, like this one along McLean Creek in Coquitlam, are harming Fraser River salmon. (Jonathan Moore)

Faulty floodgates along the Fraser River are having harmful effects on salmon stocks, according to a new SFU study.

"What we've found is a problem," said study co-author Jonathan Moore. "Many of these floodgates just don't open ... and in those locations there were fewer native fish and the water quality was poor.  

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Floodgates are small dams located along tributaries which close in order to protect fields and homes in the area, when water levels rise.

The SFU study concludes that many Fraser River floodgates are not functioning properly and preventing juvenile salmon from accessing habitat that's important to their survival. (Jonathan Moore)

However, when flooding isn't an issue, floodgates are supposed to remain open to allow fish and water to pass through. 

For the study, co-author Rebecca Seifert installed time-lapse cameras at 20 different lower Fraser River floodgates. Images captured over a six month period showed whether the gates were, in fact, functioning.

"A majority of the floodgates didn't open very much — less than 10 per cent of the day on average," said Seifert. 

Seifert and Moore say faulty floodgates impact sensitive juvenile salmon the most. 

"One of the major concerns is that it decreases the amount of nursery habitat that young salmon use —there's less habitat for them to grow up in before they get to the ocean," said Moore.

According the study, habitat around the few floodgates that did work properly wasn't negatively impacted.

A juvenile chinook salmon captured in a trap behind a Fraser River floodgate. Chinooks are one of the main species of concern. (Watershed Watch Salmon Society)

"To us, that really points to a solution of retrofitting or improving operation of floodgates so they are fish friendly," said Moore. "It feels like a potential game changer for salmon habitat in the lower Fraser."

But a quick fix may not be so easy to achieve.

A companion study out of the University of Victoria says oversight and monitoring of fish habitat that lies behind dikes and floodgates is virtually non existent.

"No one is effectively overseeing the more than 1,400 kilometres of salmon habitat behind floodgates in the lower Fraser Valley," says Deborah Curran of UVic's Enviromental Law Centre.

In July, the Fraser River sockeye fishery was closed due to low returns, while the Skeena River sockeye run was the worst in recorded history.

With files from Andrew Kurjata

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