* Feig has been Citi's forex chief for 10 years
* Will join Fortress as portfolio manager (Adds details and background)
June 17 (Reuters) - Citigroup Inc's global head of foreign exchange, Jeff Feig, is leaving the bank and will join investment firm Fortress Investment Group LLC as a portfolio manager.
Feig, who has been with Citigroup for 25 years, served as the bank's forex chief for 10 years.
"Given his tenure in his role, this departure was well-anticipated, and part of the natural cycle of the business," a Citigroup spokeswoman said in an e-mailed statement.
Feig's departure comes as Citigroup and other major banks have fired foreign exchange traders amid investigations by governments around the world into possible manipulation of currency markets.
There was no indication that Feig's departure was related to any investigation. His spokesperson declined to comment.
The investigations have resulted in dozens of traders at leading banks being suspended or fired.
Feig's departure follows that of his former boss, Anil Prasad, who left the company in February. Prasad's departure was not related to the investigations, a source familiar with the matter said at the time.
According to Euromoney magazine, Citigroup sees almost 16 percent of the estimated $5.3 trillion a day that passes through the world's largest financial market.
Spot currency trading volumes in general have fallen sharply this year, however, cooled by falling market volatility in an era of universally low interest rates and, some say, the impact of the "fixing" investigation on traders.
Feig, who joins the Fortress this autumn, will serve as the co-chief investment officer of Fortress Macro Fund.
Fortress managed $62.5 billion in assets as of March.
Feig will play a key role in furthering Fortress's evolution into a more diversified group of hedge funds centered around the Fortress Macro Fund, the investment firm said.
"His expertise ... will be invaluable as we steadily grow our business, including in the retail alternative space," said Stu Bohart, co-president of liquid markets at Fortress.
Citigroup shares were little changed at $47.93 in afternoon trading on Tuesday on the New York Stock Exchange. Fortress Investment shares were trading at $7.62. (Reporting by David Henry in New York, Patrick Graham in London and Tanya Agrawal in Bangalore; Editing by Meredith Mazzilli and Saumyadeb Chakrabarty)