LONDON, Sept 29 (Reuters) - Hedge fund Eisler Capital posted a 4.17% positive performance for the year to end-August, it said in a letter to investors, benefiting from a basis-trade strategy that has regulators worried about financial stability risks. According to the letter seen by Reuters, basis trades have been a part of the most profitable trading strategy for the $3.7 billion London-based hedge fund this year. While the fund uses basis trades in U.S. Treasuries, it also employs them with the euro, Swiss franc and Swedish government bonds, the letter showed. A Fed paper on Aug. 30 said that if these positions represent the so-called basis trades, "sustained large exposures by hedge funds present a financial stability vulnerability" warranting "diligent monitoring." The Eisler investor letter also showed the hedge fund uses swap derivatives to mitigate the riskiness of its positions.

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Persons: Eisler, Kevin Lenaghan, Nell Mackenzie, David Holmes Organizations: Eisler, Reuters, Swiss, Bank for International, Ivy Academy, Thomson Locations: Los Angeles, U.S, Europe