Peterborough kept their slim play-off hopes with a crucial win at Grimsby.
George Boyd put Peterborough ahead in the first minute of the second half, firing home from 12 yards after Nick Fenton had failed to clear the danger.
Grimsby had chances to maintain their recent good run, but were punished by Darren Ferguson's side.
Peterborough doubled their advantage and sealed the victory after 73 minutes when Alan White, on loan from Notts County, headed home Shane Huke's chip.
Grimsby: Barnes, McDermott, Whittle, Fenton (Grand 51), Newey, Till (Taylor 61), Boshell (Jones 51), Bolland, Hunt, Toner, North.
Subs Not Used: Murray, Bloomer.
Peterborough: Tyler, White, Futcher, Huke, Low, Gain, Hyde, Strachan (Butcher 63), Day, Boyd, Mackail-Smith.
Subs Not Used: Jalal, Crow, Richards, Blanchett.
Goals: Boyd 46, White 73.
Ref: R Booth (Nottinghamshire).