Shares in a French broadcaster Channel+ fell almost 16% after their debut on the London Stock Exchange on Monday.

A media holding company Life's shareholders last week agreed to merge Canal+, a production and pay-TV company known for its live sports broadcasts, and Studiocanal, maker of the Paddington film franchise.

Shares were trading around 243 British pence ($3.07) at 10:13 am London time, down 15.7% since the session opened.

Paris-listed Vivendi shares meanwhile rose 33.2% at 10:13 am London time.

"Vivendi was suffering from a conglomerate discount. So when you looked at the value of Vivendi, it was less than 10 billion euros ($10.52 billion), and the estimate of the sum of the parts was much greater than that. So to exploit that value potential of each of these assets, hence the split," Maxime Saada, CEO of Canal+, told CNBC's "Squawk Box Europe" Monday.

"(Canal+) was a very French-centric company, with about 9 million subscribers, and, in just 10 years, it has tripled its number of subscribers. Now two-thirds of our subscriber base is outside France, in Africa, in Eastern Europe, in Asia, and, of course, in France," he said.

Saada added that the merged Canal+ will seek to expand its presence as a sports broadcaster to compete with US players selectively.

"Every company I've seen in our business that really died is because they overspent on sports," he said. "We are not dependent on any type of content, any piece of content. Because we have this broad value proposition with cinema, with sports, with platforms, we can pass on the rights when we believe that they are too expensive."

Havas and Louis Hachette Group are also splitting from the Paris-headquartered media conglomerate and will be listed on Euronext Amsterdam and Euronext Growth Paris, respectively.

"We are pleased with the very high adoption rate of our spin-off project. This indisputable result confirms the strong support of our shareholders for this transformative transaction," Yannick Bolloré, chairman of the board of Vivendi, said in a statement last week after the plan. was approved, with more than 97% of votes in favor.

Canal+ London's listing was seen as a way to provide a much-needed boost to UK capital markets after a spate of exits in recent years. Chancellor Rachel Reeves on Friday described the debut as a "vote of confidence."

"I am delighted that CANAL+, a leading international media company, has chosen the UK. Their decision is a vote of confidence in the UK capital markets, the stability we are delivering and our plan for change," she said in a statement at the time.

It comes as the London Stock Exchange looks set for its worst year since the financial crisis, according to the FT report citing the LSEG, which indicates that a total of 88 companies have delisted or moved their primary listing from the main London market this year, while only 18 have joined.

The LSE's departure comes despite moves by the government and regulators to boost London's appeal as an investment center and the reform listing rules in an effort to compete with competing markets, particularly in the United States

"London's selection for Canal+ is significant as it is the largest company to join the UK Stock Exchange since changes to listing rules were made in the summer and under the new Labor government installed," Russ Mould, investment director at AJ Bell, said in an email.

"If Canal+ does well, it could act as a showcase for other big names floating in London and help fill the pot that has been depleted by acquisitions and delistings," he added.

Investors will now be closely watching the fate of other potential UK listings, including that of Singapore-based fast fashion giant Shein. The online fashion group has been involved in ongoing discussions with the British government after dropping its US flotation bid amid pressure over its ties to Beijing and wider labor practices.