Mr. Cohen's decision was made at the end of September and comes from an attempt to stem this year's losses. He now plans to keep that money on the market sidelines for the rest of the year, though he is still trading a small portfolio, along with a few other managers. The managers whose portfolios were shut are feeding Mr. Cohen short-term trading ideas, the person says.
Mr. Cohen has been one of the hedge-fund industry's most successful short-term stock-market traders, trading in and out of the market, and other traders sometimes look to him for direction. Mr. Cohen could conceivably jump back into the market quickly. Managers in cash Monday missed out on the Dow's biggest one-day point gain ever.