Said Haidar’s Jupiter Fund lost about 12% in March, paring quarterly gains to 13.4%, according to an investor letter seen by Bloomberg News. The Brevan Howard Master Fund declined 6.6% for the worst monthly loss in its two-decade-plus history, people with knowledge of the matter said, asking not to be identified discussing the returns. Diego Megia’s Taula Capital Management lost 8.6%, bringing year to date losses to 7.6%, other people said.