MANCHESTER, N.H. — Right fielder Moises Sierra buried the Sea Dogs. Again.

Sierra drilled a Blake Maxwell fastball over the left-field wall on the first pitch in the bottom of the 12th inning to lift the New Hampshire Fisher Cats to a 7-6 Eastern League victory Saturday night at Northeast Delta Dental Stadium.

The Eastern Division-leading Fisher Cats improved to 50-36 and the Sea Dogs fell to 34-53.

It was New Hampshire’s eighth walk-off win of the season and second against Portland.

Sierra’s single off Eamonn Portice in the ninth inning on May 9 gave the Fisher Cats a 1-0 win at home.

Since dropping a season-high sixth straight game in the first game of a doubleheader at home against New Britain on June 28, the Sea Dogs have gone 9-4.

“We had a tough May, we played better in June and now we’re just trying to build on that in July,” said Sea Dogs Manager Kevin Boles.

His team is now 6-4 in July.

Portland led 5-3 after four innings Saturday night, but could not hold the lead.

The Sea Dogs matched New Hampshire with 11 hits, but they also had 15 strikeouts against four Fisher Cat pitchers.

Maxwell pitched 2 1/3 innings, allowing only the one hit and striking out three.

The Fisher Cats struck first with three runs in the second inning and the Sea Dogs grabbed the lead with five in the top of the fourth.

Ryan Khoury, just back from Triple-A Pawtucket, got it going in the fourth with a leadoff single to left off New Hampshire starter Chad Jenkins.

After Alex Hassan flied out to left, the Sea Dogs came up with four straight hits. Reynaldo Rodriguez delivered an infield single, Matt Spring an RBI double, Jon Hee an RBI single and Oscar Tejeda a two-run double into the left-field corner.

Mitch Dening’s sacrifice fly to right plated Tejeda with the final run of the inning.

Travis d’Arnaud’s two-run single to center tied the game at 5-5 in the bottom of the fifth.

Portland regained the lead with a two-out rally in the top of the sixth when Dening singled in Tejeda, who had doubled.

New Hampshire’s John Tolisano quickly tied it again in the bottom of the inning when he sent an 0-2 pitch from starter Chris Balcom-Miller down the line in right for a leadoff homer.

It was still 6-6 when the Sea Dogs threatened with two outs in the top of the ninth.

After Heiker Meneses got his second single, Cliff Everts threw a wild pitch to Jeremy Hazelbaker. But Meneses was thrown out at third by d’Arnaud, the catcher, while trying to get an extra base.

The Fisher Cats had runners on second and third with two outs in the bottom of the 11th, but Maxwell struck out Craig Stansberry.

NOTES: The crowd of 8,417 was the fourth-largest regular-season crowd in Fisher Cat history. The Sea Dogs have been the opponent for each of the top four.