Young defender Greg Young has put pen to paper on a new contract with The Mariners.
The former Sheffield Wednesday centre back is considered a player for the future with the Coca-Cola League Two club after the 21-year-old made his first team debut in season 2002/03.
Meanwhile, Slade has since denied reports that he is looking to sign former Notts County striker Tony Hackworth.
The hit-man left Meadow Lane earlier this month after mutually agreeing to end his contract with The Magpies and reports last week suggested that Hackworth was set for a move to Grimsby.
Despite having Hackworth on loan at his former club Scarborough last season, Slade has denied that he had any interest in reuniting himself with the 24-year-old.
"I know there have been rumours about Tony Hackworth because I had him on loan at Scarborough, but other players are my priority at the moment," Slade told the club's official website.
"Remember, there are the players who were here last year too - I need to speak to them about their situation."
Slade also refused to speculate on the links regarding Aldershot striker Tim Sills.
