SFU research demonstrates how floodgates can undermine Fraser River salmon

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      Climate change is causing municipal governments and farmers to mitigate the effects of storm surges.

      As this year's flooding demonstrated in many areas of Canada, governments and farmers are also having to cope with higher river levels caused by rapidly melting snowpacks and extreme weather events.

      But the use of floodgates is having unintended consequences on Fraser River salmon, according to data collected through SFU's Earth to Ocean Research Group.

      In a paper recently published in the Journal of Estuaries and Coasts, scientists Rebecca E. Seifert and Jonathan W. Moore acknowledge how these barriers "play important roles in flood mitigation".

      But they also report that floodgates can "diminish habitat quality and block fish from accessing tidal creeks".

      Seifert and Moore used time-lapse photography to determine how long floodgates remained open on 22 tributaries of the Lower Fraser River. Then they compared this data to fish populations on each side.

      "Sites with floodgates that seldom opened were associated with greater differences in fish communities and with reduced upstream native species richness by about one species on average," they concluded. "Where floodgates opened infrequently, we also found lower upstream dissolved oxygen concentrations than at sites where floodgates opened for longer periods of time."

      SFU researchers examined this floodgate at Nathan Slough in the Fraser Valley, as well as 21 others. It's slightly open in this image.

      If local governments kept floodgates opened for longer periods of time, this could enhance biodiversity.

      Seifert is a marine program scientist at Environment and Climate Change Canada. Moore is an associate SFU professor of aquatic ecology and conservation.

      Meanwhile, Watershed Watch Salmon Society has commissioned a separate study through UVic's Environmental Law Centre, which raises other concerns.

      It suggests that not nearly enough research is being conducted about what's happening to fish living behind dikes.

      “No one is effectively overseeing the more than 1,400 kilometres of salmon habitat behind floodgates in the Lower Fraser Valley,” UVic law professor Deborah Curran said in a Watershed Watch news release. “It’s quite startling to see that the fish-related impacts of the over 155 pump stations and floodgates are not subject to systematic ecological review or monitoring.”

      Watershed Watch campaigner Lina Azeez called on municipal governments to build flood-protection systems in a "fish-friendly" way.

      “The technology exists," she said. "It’s the will that’s lacking.”