Nickelodeon is losing a longtime executive at the top of its ranks.

Russell Hicks, president of content development and production for the Nickelodeon Group, is stepping down after 18 years at the company.

“Russell Hicks has decided to step down from his position effective immediately,” a spokesperson for Nickelodeon on Tuesday told The Hollywood Reporter. At this time, there are no plans for him to be replaced.

Related Stories

In his role, Hicks managed the company’s live-action, animation development and production teams for all of Nick’s content platforms, which include Nickelodeon, Nick at Nite, Nick Jr., TeenNick and Nicktoons. Before he was upped to president in 2012, he served as Nick’s chief creative officer. 

Hicks’ departure comes amidst turmoil at Viacom’s networks: Comedy Central, TV Land, VH1 and MTV all have undergone executive shakeups within the past two years.

Here’s the internal memo from Cyma Zarghami, president of Viacom Kids & Family Group, that went out Wednesday:

I wanted to share with you the news that Russell Hicks has decided to step down from his position at Nickelodeon.

For the last 18 years, Russell has been an incredible creative partner not just to me, but to our entire organization, first as Chief Creative Officer, but especially during these last four years, in which he served as our President of Content Development and Production.

Though it is hard to have to say good-bye to someone who has been such a fixture at the company, and a friend, this transition comes at a time when the Nickelodeon brand truly is in a position of strength.

Since moving to the West Coast in 2012, Russell expertly shepherded our terrific development and creative teams to some of our greatest creative successes. Our content pipeline at the moment is the most full and varied it has ever been.  Our relationships with the creative community have never been as deep as they are today. And we have a schedule of hits, in every genre, across all of our platforms.

All of our great work has put us back at number one–with preschoolers, with kids 2-11, and as of the end of May, with kids 6-11 once again. In fact, our just-launched show, The Loud House, which originated from our shorts program, is already the top animated kids’ show on TV, joining SpongeBob and Alvinnn! to lock up the overall top three.

The current temporary structure for our teams will remain in place while we regroup and formulate the right plan for going forward.

I hope you will join me in wishing Russell all the best and thanking him for his immeasurable contributions to Nickelodeon; I know we will miss him.  I could not be more proud of all of you and all the great work at Nickelodeon right now.

–Cyma

This article was updated on June 8, 2016 at 11:20 a.m. with the internal memo above.