Directors of the Massachusetts state pension fund voted Tuesday to give executive director Michael Trotsky responsibility for a second job: chief investment officer of the $50 billion fund. It is the first time in memory the board has voted to combine the positions, officials said. Treasurer Steve Grossman, who is chairman of the fund board, insisted the move was “not setting a precedent for the future,’’ but rather was serving a need in the present.

Trotsky, 49, has been executive director at the Pension Reserves Investment Management board for two years. He took on the additional role of investment chief in June, when longtime staffer Stanley Mavromates left for a job in the private sector. A former hedge fund manager, Trotsky has from the outset had his hands in the investment operations more than many of his predecessors.

The pension board for years has struggled to compete for talent in Boston, where a large financial services industry provides higher pay. The new arrangement would have the dual effect of filling an important job that could take months to fill through a standard executive search and saving the pension fund money. Trotsky has agreed to take on the second job for a $50,000 raise, for a total of $295,000. That means the state can save the remainder of the $245,000 previously devoted to the investment post.

Officials at the meeting Tuesday said the pension fund has returned more than 9 percent for the year through the end of September. That’s for a diverse portfolio of stocks, bonds, and alternative investments. The Standard & Poor’s 500 index is up 16.8 percent so far this year.