Co-founders David Pendlebury and Richard Conyers set up Harmonic in 2002 after leaving rival Aspect Capital, and use computer algorithms to bet on macroeconomic trends using currencies, commodities, fixed income and other assets.

Co-Chief Executive Officer Romael Karam, who joined Harmonic in 2003 and currently shares the day-to-day running of the company with Pendlebury, will assume full CEO responsibilities in July, working with the five remaining partners, said the spokeswoman.

Pendlebury and Conyers "will remain materially invested in Harmonic's products well beyond July 2016 with an appropriate level of economic interest in the future profitability of the business", the spokeswoman told Reuters, without giving details of the new ownership structure.

Harmonic clients were aware of the management change, she said. She declined to give a specific reason for the move, but said neither co-founder had any immediate plans.

The move follows news this week that Nevsky Capital's Martin Taylor and Nick Barnes were closing their high-performing fund and leaving the industry.

The Harmonic Alpha Plus Macro Fund - U.S. Class was up 0.5 percent between January and Dec. 18, 2015, performance data seen by Reuters showed. That compares with an average performance for all Global Macro funds of minus 1.75 percent in the year to end-November, data from industry tracker eVestment showed.

(Editing by Susan Fenton)

By Simon Jessop and Maiya Keidan