Anglo-Swiss firm Stone Milliner, set up in 2012 by former Moore Capital portfolio managers Jens-Peter Stein and Kornelius Klobucar, averaged returns of 8.3 percent between 2014 and 2016, a source told Reuters, while Moore Capital Management averaged 3.4 percent, a second source said.

London-based Gemsstock, set up in January 2014 by Moore Capital trader Darren Read and his co-founder Al Breach, made 12.8 percent on average over the same period, documents seen by Reuters showed.

Chris Rokos, a Brevan Howard alumnus, raised another $2 billion in February after returns of 20 percent in 2016.

EDL Capital made gains of 18.4 percent last year after ex-Moore Capital trader Edouard De Langlade launched the firm in September 2015, according to a source close to EDL Capital. It has amassed assets of $450 million to date, he said.

Ben Melkman, who also formerly worked at Brevan Howard until May 2016, raised over $400 million for his launch in March, SEC filings showed.

Brevan Howard's firm-wide assets fell to $14.6 billion in 2017, from $37 billion in 2012.

Rush For Macro

But the old guard are fighting back. Some have been cutting fees and offering alternatives.

Howard, Brevan Howard's co-founder, last month launched a new fund managed solely by him, which sources said has already amassed more than $3 billion.

Tudor Investment lowered its management fees to 1.75 percent and performance fees to 20 percent in February after a reduction last year and Moore Capital cut the management fee on its Moore Macro Managers fund to 2.5 percent from 3 percent.