The firm has cut more than a dozen employees, according to The Wall Street Journal , citing a person close to the situation. The source added that Citadel's main fund has fallen 6.5 percent year-to-date.
The Journal reported that the job cuts happened at Surveyor Capital, a division of Citadel. The publication added that Surveyor had roughly 200 employees before this announcement.
Hedge funds as a group had a tough 2015, posting their worst year since 2011, according to investment research firm Eurekahedge.
CNBC has reached out to Citadel for comment.