Fortress Investment Group reported a fourth-quarter operating loss of $258 million after writing down the value of private-equity assets and setting aside money for fee refunds.

The loss, excluding some Costs, was 56 cents a share, compared with a profit of $78 million, or 18 cents, a year earlier, the company said yesterday in a statement. Fortress was expected to earn 1 cent a share. Shares rose as much as 41 percent.

Investment managers including Blackstone Group and KKR have marked down their investments to match a global decline in prices. Fortress said results included $299 million of reserves for a potential “clawback” of fees by clients and impairment of holdings. Assets under management fell 14 percent during the quarter to $29.4 billion.

Hedge funds lost 19 percent on average last year, the worst performance for the $1.2 trillion industry since 1990, according to Hedge Fund Research Inc.

Fortress rose 38 cents, or 25 percent, to $1.88 in trading.