Jon Gillies made 24 saves for Calgary (32-23-9), which trails the Anaheim Ducks by one point for the second wild card into the playoffs from the Western Conference. The Flames are also two points back of the Los Angeles Kings for third in the Pacific Division.
"I thought it was a pretty good effort but you can't hang your hat on a pretty good effort," Calgary defenseman Travis Hamonic said. "We've got to gain some ground."
Shore put Dallas up 1-0 with 39 seconds remaining in the first period when hesitated before shooting by Gillies. The goal came 2:14 after Shore hit the post.
"Goals are going to happen," said Gillies, who received his first loss in six NHL games (3-1-0). "Good ones, bad ones, it doesn't matter. Just have to reset and go forward."
Seguin scored on the power play to make it 2-0 at 10:04 of the second period when he took a pass from Jamie Benn and shot over Gillies' shoulder. Seguin has four points (three goals, one assist) in his past three games.
Brett Ritchie was stopped 11 seconds later by a sprawling Gillies after a setup by Alexander Radulov. Ritchie also hit the post at 17:31.
Bishop made consecutive saves on Matt Stajan at 18:57 and 18:59 of the second period. He also made glove saves on Dougie Hamilton at 10:58 and Sean Monahan at 11:05 of the third period, and stopped Matthew Tkachuk with 11 seconds remaining.
"We've got to find a way to score," Flames captain Mark Giordano said. "That's it. That's the difference tonight."
