GATESHEAD'S Blue Square Bet Premier play-off hopes are all but over after defeat in Lincolnshire saw them slip to 10th in the table.
The depleted Tynesiders were undone by two inswinging Frankie Artus corners, one in each half, that were headed home by Shaun Pearson.
That second, 11 minutes into the second half, killed off Gateshead, who carried little goal threat and are now six points from the play-offs with four games left.
“It was a poor performance and we played with no real purpose,” said Gateshead boss Ian Bogie.
“We weren’t at our best and didn’t do enough to win.”
A Jamie Chandler foul on Artus saw Conor Townsend’s 16th-minute free-kick cleared for a corner which brought the Mariners opener.
Pearson stopped to head home after Artus had swung the ball into the near post, The Heed having conceded from a corner in their 1-0 defeat at Newport in their last away game.
Jon Shaw had a shot deflected wide off Simon Church before Paul Farman had to save from Pearson following another Town corner.
The game could have turned on the half-hour when Josh Gillies was taken out just inside the box by Gary Silk, but Middlesbrough referee Ross Joyce inexplicably failed to point to the spot.
Shaw had a shot blocked early in the second half, and the Mariners doubled their lead four minutes later through Pearson’s second.
On-loan Newcastle defender Paul Dummett headed Artus’ corner into the face of Pearson, the ball rebounding into the net.
Gateshead rarely looked like getting back into the game, Town goalkeeper James McKeown having an untroubled afternoon.
Ben Clark had a shot blocked by Craig Disley, while Michael Coulson and Liam Hearn were wide at the other end.
Bogie introduced pace pair Yemi Odubade, after an eight game lay-off, and James Marwood on the hour in an attempt to galvanise his side.
It was Grimsby, beaten 1-0 on Tyneside back in August, however, who went close to making it three ten minutes from the end.
Hearn’s cross saw Farman make a fine reaction save from Mariners substitute Andi Thanoj.
Former Gateshead loanee Peter Winn, looked a certain scorer but he blasted the ball against the underside of the bar.
GRIMSBY TOWN: McKeown, Silk, Pearson, Townsend, Miller, Church (Thanoj 74), Disley, Artus, Coulson, Hearn, Hughes-Mason (Winn 72) Subs not used: I’Anson, Soares, Duffy.
Goals: Pearson (15, 56) Bookings: Pearson (17).
GATESHEAD: Farman, Baxter, Rents, Gate, Dummett, Clark, O’Brien (Moore 81), Chandler, Shaw, Gillies (Marwood 61), Cummins (Marwood 61) Subs not used: Odhiambo, Deasy (gk, Moore.
Booking: Rents (26).
Referee: Ross Joyce (Middlesbrough) Att: 2,938.