Fisher, who scored 32 seconds into overtime Thursday night a 3-2 win over the New York Islanders, restored Ottawa's lead 3:44 into the second period with a goal.
Kovalev scored his first Senators goal 43 seconds in, and Jarkko Ruutu added Ottawa's second goal 1:42 later to open up a 2-0 lead 2:25 into the game.
Chris Neil also scored, and Brian Elliott made 27 saves in his first start of the season for Ottawa (3-1).
RED WINGS 3, CAPITALS 2
In Detroit, Thomas Holmstrom broke a tie with a power-play goal with 6:53 left in the Detroit Red Wings' victory over the Washington Capitals.
Ville Leino and Jason Williams also scored for Detroit, Valtteri Filppula had two assists, and Chris Osgood made 21 saves. Matt Bradley and Brendan Morrison scored for Washington, and Jose Theodore stopped 34 shots.
DUCKS 3, FLYERS 2 (SO)
In Philadelphia, Teemu Selanne scored the only goal in a shootout, and had two goals in regulation to lift Anaheim to a win over Philadelphia.
Selanne scored twice in third, including the tying goal with only 16 seconds left. He beat Flyers goalie Ray Emery from the post to send the game into overtime.
PENGUINS 5, MAPLE LEAFS 2
In Toronto, Sidney Crosby scored two power-play goals, and Evgeni Malkin had three assists to help the Pittsburgh Penguins beat the winless Toronto Maple Leafs.
Crosby's goals, both set up by Malkin, came in the second period to put the defending Stanley Cup champions up 4-1 and erase any hopes the hosts might have had of mounting a comeback.
LIGHTNING 5, HURRICANES 2
In Tampa, Fla., Ryan Malone had three goals, including a go-ahead score midway through the third period, and the Tampa Bay Lightning beat the Carolina Hurricanes.
Malone completed his hat trick on an empty-netter with 1:16 remaining.
BRUINS 4, ISLANDERS 3
In Boston, Blake Wheeler and Marc Savard scored in the shootout after the Boston Bruins rallied for three goals in the final 8:01 of regulation to beat the New York Islanders.
Jon Sim, Radek Martinek and John Tavares scored second-period goals for the Islanders.
DEVILS 3, PANTHERS 2
In Sunrise, Fla., David Clarkson scored a power-play goal with 3:35 left to give the New Jersey Devils victory over the Florida Panthers.