Neither the company, which announced the changes late on Tuesday, nor El-Erian gave a reason for the departure, schedule for mid-March. El-Erian was seen as heir apparent to Pimco co-founder Bill Gross.

Customers withdrew $41.1 billion of money from Pimco's flagship Total Return Fund last year, a record amount for the $2 trillion manager, according to investment research firm Morningstar.

"Things don't appear to be going that well," one trader said, citing the high outflows. "The departure is an irritant and everything together is bound to chip away a bit at the share price," he said.

Analysts said El-Erian was the public face of Pimco alongside Gross and played an important role in the successful marketing of Pimco's funds. "It is not easy have two Co-Chief Investment Officers," said one analyst who declined to be named, referring to the dual role of El-Erian and Gross at the firm.

(Reporting by Jonathan Gould and Kirsti Knolle, Editing by Thomas Atkins)