The addition of Treanor means the Marlins have one vacancy to fill on manager Don Mattingly's staff. They are searching for a replacement for Shine as administrative coach and video replay coordinator.
Treanor has a previous connection with Marlins vice president of pitching development Jim Benedict, who joined Miami in 2015 after working with the Pirates.
Treanor, who replaces Reid Cornelius, will work closely with pitching coach Juan Nieves.
A pitcher during his playing days at Cal Poly San Luis Obispo in California and in the Minor Leagues, Treanor previously managed in the Marlins' system from 2002-03 and 2005-08. Since 2011, he has managed Triple-A Indianapolis with Pittsburgh.
The Marlins made three coaching changes immediately after the season. They did not retain Cornelius, hitting coach Barry Bonds and third-base coach Lenny Harris.
Mattingly's staff now includes Nieves, Treanor, Tim Wallach (bench), Mike Pagliarulo (hitting), Frank Menechino (assistant hitting), Fredi Gonzalez (third base), Lorenzo Bundy (outfield/baserunning), Perry Hill (first base/infield), Brian Schneider (catcher) and Jeff Urgelles (bullpen coordinator).
Shine excelled as a replay coordinator, and his recommendation for challenges led to a number of overturned calls. He spent three seasons with the Marlins.
A native of Spokane, Wash., Shine accepted the opportunity with the Mariners, where he will be closer to home.
The Marlins have also made a front-office change, parting ways with David Keller as director of pro scouting.
Joe Frisaro has covered the Marlins for MLB.com since 2002. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.