The Liverpool-born striker, 26 on Wednesday, is near the top of the EVO-STIK NPL's Premier Division goals-coring charts having bagged nine goals already this season.
Mitchley, who signed for Marine manager Sean Hessey on Monday, boasts a prolific record in recent seasons, having scored 65 times in 102 games for Skelmersdale and his previous club Kendal Town.
After kicking off his youth career at Skem he was snapped up by Blackpool, making his professional debut in October 2008 as a late substitute against Crystal Palace.
Skem signing Danny Mitchley
Loan spells followed at Southport, Burscough and Wrexham before he moved on to Mansfield Town in November 2010. Another switch to Altrincham in the summer of 2012 led to a loan spell at Marine, where he scored twice in four appearances.
A second loan took him to Kendal Town where 10 goals in 11 games led to a permanent move to the Mintcakes before he returned to Tommy Lawson's Skem last season.
Hailing Mitchley's arrival, Marine chairman Paul Leary said: “I’m absolutely delighted that Danny has agreed to join us on a contract until the end of next season.
"Since becoming chairman in 2004 I think that he is the most high profile signing we have made, and hopefully will provide the goals to push us towards the play off positions.
"I congratulate Sean in being able to persuade a player of Danny’s calibre to come to the Marine Travel Arena and look forward to him scoring plenty of goals for the Mariners.”
Hessey said: “I really am over the moon to have brought Danny on board. We’ve not scored as many goals as we’d like and when quality players become available you have to try to get them, Danny will give us that firepower as his record speaks for itself and I know from playing against him that he’s a real handful."
He added: "It’s a statement of our intent too, the club have backed us to bring him in and hopefully we can start to score more goals and move up the table.”
Follow us: @evostikleague on Twitter | The NPL group on Facebook by clicking here: www.facebook.com/groups/TheNPL/
Keep up-to-date with our exclusive email newsletters.
Subscribe