Large commodity trading advisors (CTAs) focusing on currencies suffered back-to-back monthly losses for the first time this year, according to the Barclay Group, which tracks fund performance.

The firm’s BTOP 50 Index, which reflects the performance of the largest currency funds, posted a net loss of .99 percent through Aug. 29. The index lost a marginal .14 percent in July after gaining ground in both May and June. On the year, the index is down 1.95 percent.