Brian McManus, head of collateralized debt obligation research at Merrill Lynch, and a frequent Insitutional Investor Fixed Income All-America Research Team winner, has retired to Miami. Dan Castro, the asset-backed securities research chief, says he is filling in for McManus. He says there are no immediate plans to replace him. Castro adds that McManus, 44, likes to travel and owns property in Eastern Europe and Nicaragua. At Merrill, he reported to Marty Fridson, managing director and chief high-yield strategist. Fridson did not return calls. McManus did not reply to e-mail messages.