NEW YORK, Jan 11 (Reuters) - Hedge fund powerhouse Citadel, which oversees $30 billion, folded its Fundamental Strategies unit into two other businesses and laid off a portfolio manager, people familiar with the matter said on Friday.

Michael Doniger, director of research and a portfolio manager at Citadel Fundamental Strategies, was let go this week, the sources said. Citadel folded the Fundamental Strategies business, led by Eric Felder, into Aptigon Capital and Global Credit, two other businesses also headed by Felder.

Felder joined Citadel in 2017 as senior managing director in charge of Fundamental Strategies. Last year he took over responsibility for managing Aptigon, one of Citadel's stock-picking businesses.

Felder oversees roughly two dozen portfolio managers.

A Citadel spokeswoman declined to comment. Doniger could not be reached for comment.

Citadel's main multi-strategy fund returned 9.1 percent last year when the average hedge fund lost money. (Reporting by Svea Herbst-Bayliss; Editing by Will Dunham)