Pier weren't at their fluent best, but managed to take the lead when neat link-up play down their right between Billy Logan and Chris Nelson led to Logan's cross being met by Sam Garnett at the back post.
It was all square at the break though, Fishermen grabbing a leveller after a scramble in the Pier box from a corner.
The crucial moment came when Fishermen spurned a glorious chance to take the lead, Pier hit them on the counter-attack and after winning a free-kick on the edge of the box, a Fishermen man was sent off after receiving his second yellow card.
Billy Logan's drilled free-kick was cleared out to Shaun Dodson, who fired into the top corner with a left-footed effort from the edge of the box.
Pier took charge from there on in and Martin Cooper grabbed a brace to hand them a 4-1 win against a Fishermens side who they meet in a huge North Riding County FA Saturday Challenge Cup semi-final next week.
Boss Andy Spivey said: "We weren't at our best but we managed to get over the line. We're expecting a tough game in the semi-final next week."
Nelson was Pier's man of the match.
Edgehill suffered a 3-2 home defeat against Hunmanby United as striker Cameron Dobson smashed in a superb match-winning hat-trick.
Danny White's foul in the box led to United's opener after 20 minutes, Dobson netting from the spot.
Dobson's second handed United a 2-0 lead at the break, but Edgehill improved after the break and were back in the game when Chris Duley spectacularly fired into his own net.
Star man Dobson completed his hat-trick with a neat finish into the bottom corner before Edgehill replied with a penalty of their own through Danny Collins after Lloyd Henderson was felled in the area.
United held on for the win though and Edgehill boss Steve Clegg conceded the visitors were good value for their win.
He said: "They deserved to win the game, they just about edged it and Dobson was by far the best player on the pitch."
Newlands' bid to retain their title received a boost with a 5-1 win at Westover Wasps.
Ben Luntley grabbed two and goals from Dan Freer, Liam Cooper and a Sean Exley pen rounded off the win for Shaun Mancrief's side.
Michael Wilson shone in the Park midfield while Jamie Gallagher also put in a decent performance.
Seamer were held to a 3-3 draw on the road at Sleights.
Sleights led 2-0 at half-time before two penalties brought Seamer level. Their first was converted by Luke Delve before Dan Bradbury fired in their second.
The home side looked to have won it late on, but Luke Purvis smashed in a last-gasp leveller to seal a point for Paddy Parke's side.