Amon has been a target for several rival clubs this year, with Hawthorn emerging as a leading contender for the winger.
As an unrestricted free agent, Amon will be able to walk to his club of choosing without a matched bid by the Power.
“Karl has been an outstanding clubman in his time with us and he should be commended for his professionalism and maturity this season in particular,” Port Adelaide list manager Jason Cripps said.
“The club and Karl remained in continual discussion around his future throughout the season, yet his dedication to his preparation and application on game day never wavered.
“We wish him well in the next stage of his career.”
Amon will be able to exercise his rights as a free agent from Friday, October 7.
A former Lion, Mayes joined the Power in 2018 and end his stint at Alberton after 20 games, tallying 121 matches in his career.
Another ex-Brisbane player, Skinner joined the Power ahead of this season as a delisted free agent after three games as a Lion.
Skinner impressed in his 2021 campaign with South Adelaide, gaining the attention of Port Adelaide.
Schofield joined the Power as a father-son selection in 2020 was unable to make his AFL debut.
“It is always a difficult time when we have to farewell players from our list, especially people of the character of Sam, Taj and Sam,” Cripps said.
“Mayesy has always done the team thing, playing across all three lines as needed, and has been a really positive influence on some of our younger players as a leader in our SANFL program.
“Taj played some strong footy earlier this season but like Sam (Skinner), opportunities to play in the AFL side were limited.
“We thank all three boys for their dedication to our club and wish them every success going forward.”