"We regret that we cannot offer him a contract extension, but it was felt that a new voice would benefit the club.
"Colm came into the senior side as coach in a time of some instability and he steered the panel with great skill to point where they were just a kick of a ball from a semi-final place in his first season.
"He has worked extremely hard for the club and his admirable work ethic is unsurpassed."
Shannon claimed a much-needed 28-18 victory over Dolphin at Coonagh last Saturday, with the result seeing them leapfrog over local rivals Garryowen to finish seventh in the table and book their place in next season's ten-team Division 1A.
It was also announced that the club's assistant coach and video analyst Ger Casey will not be seeking a return to his position.
Keane gave his appreciation to Casey, adding: "Ger is another talented coach who along with Colm helped guide Shannon's Under-20 side to All-Ireland glory a few years back, and their working relationship and skills benefited many players in the club.
Shannon RFC will now begin the process of finding a suitable replacement for Tucker and filling the other positions within the coaching structure.
With no further involvement in this season's Ulster Bank League, that process will now be the main focus for the Executive Committee.
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