The president of the Nickelodeon Group -- a 30-year veteran of the company -- will be replaced on an interim basis by Sarah Levy, COO of Viacom Media Networks. In the coming months, the company looks to kick off its largest-ever number of TV shows, totaling more than 800 new episodes.

Zarghami joined Nickelodeon in 1985 and was named president in 2006.

Although Nickelodeon continues to have the greatest share of total viewing in kids' television, its viewership has declined, alongside other kids' networks. For the 2017-2018 TV season, the Nickelodeon network averaged around 1.31 million viewers, with Disney Channel at 736,000 viewers and Cartoon Network at 636,000 viewers.

From June 2017 to June 2018, the Nickelodeon network pulled in $371 million in national TV advertising, according to iSpot.tv. Total national kids TV advertising revenues haver remained constant at around $1 billion in recent years, according to estimates.

For months, Viacom has been in the middle of possible re-merger talks with CBS Corp. That effort has hit a roadblock, due to CBS' and controlling shareholder National Amusements' legal actions against each other.

National Amusements is also a majority shareholder of Viacom.