The losses were disclosed in investor documents reviewed by Business Insider.
That implies that investors are pulling money from Rubicon also. Ross Gillam, a spokesman for Rubicon at external PR firm Instinctif Partners, didn't respond to a request for comment.
In a July letter to investors reviewed by Business Insider, founder Paul Brewer attributed about half of the year's losses up until that point to wrong way bets on currencies. The fund had lost 27% after fees through mid-July, and has only added to losses since.
In a letter to clients this week, Rubicon did not explain what had caused the more recent losses.
The fund did say that it believed prices for dollars would increase in coming months, however.
The performance marks a sharp turnaround from last year, when the fund gained 7.3%, according to the investor document. It also stands in sharp contrast to other so-called macro hedge funds, which are breakeven for the year through August, according to data from HFR.
A newer fund that the firm runs, meanwhile, the Rubicon Dynamic fund, is up 13.14% this year through end of August, according to investor documents. Those gains were mostly on bets from emerging markets. The fund launched in February 2016.