The pair had won bronze medals at the previous two legs in London and Kazan, but in Canada they improved their score significantly, finishing with 325.92 points.
They were only two points of winning gold, with China’s Yajie Si and Jie Lian collecting 327.90 points.
Home favourites and Commonwealth Games champions Meaghan Benfeito and Roseline Filion came third with 317.28 points.
Afterwards Couch and Barrow’s coach Andy Banks tweeted; “Over the moon with what I think is the girls’ best performance ever.”
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