The Mariners came into the clash with the U’s knowing a draw or better would guarantee EFL football for next season with two games still to play but they fell behind after just five minutes to Tom Hopper’s early goal.

Town showed signs of promise either side of half-time but were unable to find an equaliser and John Akinde struck with 11 minutes remaining to ensure the points stayed in Essex as Colchester boosted their own bid to stay in the division.

Harry Clifton replaced Gavan Holohan and Donovan Wilson came in for Danny Rose as Grimsby head coach David Artell made two changes to his starting XI following the 3-0 win at Crewe Alexandra on Saturday.

Jake Eastwood was in goal, with Toby Mullarkey, Doug Tharme and Harvey Rodgers forming the back three.

Liam Smith and Charles Vernam took up wing-back positions as Clifton moved into central midfield alongside Curtis Thompson and Kieran Green.  Wilson was joined by Justin Obikwu in attack.

The away substitutes were Seb Auton, Denver Hume, Niall Maher, Callum Ainley, Abo Eisa, Harry Wood and Jamie Andrews.

Colchester started the evening one place and five points behind the Mariners in the league table.  Danny Cowley’s side were also just a point ahead of Sutton United in the battle to avoid the drop into the National League, albeit having played two games fewer.

Striker Akinde replaced Noah Chilvers in the only change to their team after the weekend’s away victory at Crawley Town.

A free kick from Smith on the right was eventually cleared as Town were the first to attack.

But it was the hosts who opened the scoring from their first chance of the game on five minutes.  Arthur Read sent HOPPER clear with a defence-splitting ball through the middle and the striker calmly clipped it over the advancing Eastwood.

Akinde saw a shot blocked after linking up with Hopper, before Green was brought down by Jay Mingi to give the Mariners a free kick in a dangerous position on the left.  They were not able to make the most of it though, as Vernam’s delivery went out at the far post for a goal kick.

Tharme’s first long throw into the penalty area of the evening was ruled to have come off the head of Green and gone out for a goal kick as the Town players appealed for a corner, then a home free kick was dealt with as Obikwu brought the ball clear.

Colchester goalkeeper Sam Hornby gathered a deflected low cross from Vernam after a free kick had dropped for the wing-back, before an interception by Mingi gave the visitors their first corner, which was headed clear.

Cameron McGeehan fired just wide from 20 yards and a good challenge by Rodgers stopped Mingi on the right as the home side looked for a second goal.

Town were yet to test Hornby as the half-hour mark passed, although Wilson did well to work his way into the box and hit a shot which took a deflection on its way past the post for a corner.  Vernam’s flag-kick was claimed by the keeper.

Great defending at the other end by Tharme saw him head off the line from Jayden Fevrier and the resulting corner was also cleared as the Mariners’ deficit remained at one goal.

A foul on Hopper gave Colchester a free kick midway inside the Grimsby half on 35 minutes and the delivery into the box initially looked to have caused problems but the ball was eventually cleared by Obikwu.

The home pressure continued with a corner on their right and Thompson was first to it to head behind for another one on the left.  This time, McGeehan’s delivery beat everybody and bounced out at the far post for a goal kick.

Another good tackle by Rodgers stopped Fevrier on the right edge of the box, before a Wilson pull-back at the other end was cut out for a corner by Tom Dallison after the striker had got past Hornby.  The ball from the flag did not lead to a chance in front of goal.

Dallison blocked a strike by Vernam from 18 yards as Town kept looking to get themselves back on level terms before half-time.

Three added minutes were played at the end of the first half and the Mariners had a great chance to get their equaliser when a clearance from Hornby was charged down by Obikwu.  The ball ricocheted to Green and he played it back to Obikwu but the striker was denied by an excellent challenge from Mingi.

That meant although Town had shown some promising signs towards the end of the half, Colchester’s single-goal advantage remained intact at the interval.

Chilvers replaced Alistair Smith for the hosts before the restart and an early shot on the turn by Wilson flew over the bar after a cross from Smith on the right.

Obikwu was shown the first yellow card of the game after he was adjudged to have dived following a challenge by Dallison inside the box.

Defender Connor Hall made an important header after Green had chipped a cross towards Smith, then Eastwood did well to race off his line at the other end and beat Chilvers to a through-ball.

Town had started brightly after the break and a long ball from Mullarkey was headed down by Green inside the penalty area but Wilson was unable to reach it and Hornby gathered.

A low effort from distance by Clifton was blocked, before Colchester were inches away from doubling their advantage when a low strike across goal by Fevrier hit the outside of the post following a quick counter-attack.

Town were enjoying long spells of possession as the hour mark passed, with the home side content to wait for attacking opportunities on the break.

Wood replaced Thompson in the away side’s first change on 66 minutes, before another perfect sliding challenge by Rodgers brought a home attack to an end as this time, the defender stopped a strong run by Akinde.

Fevrier beat Vernam to a ball flashed across the Colchester six-yard line before bringing it clear in an eye-catching run to halfway, then Chilvers set off down the left but was unable to cause a problem after he slipped under contact from Green.

Clifton went the closest yet to a Town equaliser when his glancing header from an Obikwu cross dropped just wide of the far post, with keeper Hornby then booked for time-wasting over the goal kick.

Wood conceded a corner at the other end soon afterwards but the ball from the flag was headed away.

Ellis Iandolo was booked for bringing Clifton down after the midfielder met a cross-field ball from Wood on 75 minutes.  Vernam’s free kick was headed back across goal by Mullarkey but nobody in the red of the Mariners could force the ball towards the net.

A foul on Akinde brought a free kick for the hosts a minute later, although the offside flag went up when Read’s delivery was headed on inside the box.

Eisa replaced Smith with 12 minutes to go and the substitute took up a position on the left as Vernam switched to the right.

But a minute later, the hosts doubled their lead when a misplaced clearance was worked back to AKINDE on the edge of the box and he floated a cross-shot into the far corner of the net.

Hornby tipped a 20-yard effort from Wood over his bar for a corner as Town looked to respond, before Akinde walked off the pitch to be replaced by Riley Harbottle for the last eight minutes.  The flag-kick was cleared from danger.

A shot by Chilvers was blocked for a corner just before the game moved into at least six minutes of added time and the ball was played short from the flag as Colchester aimed to run the clock down.

Hornby got down to stop a low effort from Clifton at his near post as Town aimed to haul themselves back into the contest.

Colchester were then reduced to 10 men for the closing seconds of the match as Dallison was shown a straight red card for a poor challenge on Obikwu.

Jayden Richardson replaced Fevrier in the final substitution of the evening before the free kick from Vernam, which was well-saved by Hornby.

That proved to be Town’s last chance to pull a goal back as Colchester saw out the remaining seconds to seal their victory and move themselves four points clear of 23rd-placed Sutton.

The Mariners remain six points ahead of the bottom two with two games to go and with goal difference still in their favour, they will now look to confirm their place in League Two for next season when they host Swindon Town at Blundell Park in their final home fixture of the campaign on Saturday.