James Simons, a mathematics professor and one of the highest paid hedge fund managers, is retiring as chief executive of his Renaissance Technologies firm on 1 January next year, media reports said.

Mr Simons will remain as a nonexecutive chairman, and will keep his money in the funds, according to the letter obtained by Reuters. Current co-Presidents Bob Mercer and Peter Brown will become co-CEOs in January, the letter said.

One of the most successful managers in an industry that suffered heavy losses last year, his estimated net worth stood at around $8 billion in March.

The $5.5 billion Renaissance Institutional Equities Fund is down about 9 per cent for the year, and fell 16 per cent last year, Reuters said. The $2.5 billion Renaissance Institutional Futures Fund is up about 1.6 per cent this year, but fell 9 per cent last year.

Simons worked as a code cracker for the US National Security Agency and taught math at Harvard University and the Massachusetts Institute of Technology before heading the math department at the State University of New York at Stony Brook.