The club confirmed the Portuguese attacker would not be extending his contract, instead leaving Australia to pursue an opportunity elsewhere.
It comes after speculation the 27-year-old was set to head south to Western Sydney after two and a half seasons in Gosford and a previous stint in Adelaide.
"This is a good opportunity for me but at the same time it's sad because I love Australia and the Mariners have been very good to me," Ferreira said.
"The club, the fans, the office, the coaches, the players and everyone has been great so it's mixed feelings right now."
Ferreira, who shifted from the wing to a playmaking position under first-year coach Paul Okon this season, is a loss for the Mariners.
The club have already reluctantly farewelled prolific striker Roy O'Donovan to Newcastle and first-choice goalkeeper Paul Izzo to Adelaide.
At the very least it gives Okon the opportunity to shape his own squad for next season.
The former Socceroo left for Europe this week on a scouting trip to further grow a youthful team that showed glimpses of talent on their way to an eighth-place finish.