Hedge fund managers who are still hung over from the market's August bender now have something else weighing heavily on their minds: Bonuses. How small will they be? What if the market stays flat for the rest of the year? What's 20 percent of nothing?

Just as portfolio managers are scrambling to make bets on the next big performer, hedge fund watchers are betting on the bonus pool. Hedge funds make money from investors in two ways: by charging a fee based on assets under management, usually about 2 percent, and by taking a portion of the profits it makes, usually about 20 percent. It's the latter that typically determines bonuses.

Options Group, a consulting firm that tracks hiring and compensation trends, predicts that hedge fund bonuses will fall by 5 percent to 10 percent from their 2006 levels, which were up about 15 percent from the prior year.

But Glocap Search, a Wall Street recruitment firm that publishes the annual Hedge Fund Compensation Report with Lipper HedgeWorld, is a bit more optimistic. According to Adam Zoia, the report's editor, bonuses for the hedge fund industry overall will likely rise by 8 percent or 9 percent during 2007.

That's about half the amount he was forecasting for bonuses before the past two months of market turbulence but still pretty good considering the recent beating stocks have taken.

Bonuses will not fall further, Zoia says, because hedge fund owners don't want to risk losing valuable employees during a down year. The top echelon is more likely to subsidize the bonus pools from their own pockets in order to retain talent.

"In broad terms, the owners may get paid less," Zoia says. "But they are able to act as the shock absorber for the rest of the fund. It's in their best interest to do so."

But hedge fund owners could end up coughing up part of their own compensation to another dissatisfied constituency: their investors.

While many funds collect an incentive fee from investors on an annual basis, plenty of others choose to collect them twice a year or even quarterly. The fee is typically 20 percent of any profits the funds make during a 12-month period, whether collected once, twice, or four times during those 12 months.

This means that if investors paid 20 percent on profits from a strong first half of 2007 which then were erased during the second half, the fund may be obligated to return the incentive fees it already received.

Deephaven Capital Management, a hedge fund controlled by Knight Capital Group, told its investors late last month that it is prepared to return "a substantial portion" of the $68.4 million it already collected from them if the funds lose money during the second half of the year. At the end of the year, investors will be obligated to pay only 20 percent of the total return for the funds.

Much of that $68 million, should it go back to Deephaven investors, will be recouped from the fund's managers, who have already taken it as compensation. While the Deephaven funds suffered a blow during August, they are not under water for the year, according to an investor. One is up 5 percent year-to-date, and the other is flat.

Still, plenty of hedge fund managers will keep a close eye on the year's total return figure as they look to carefully avoid blowing the windfall they made earlier this year.

While no other hedge funds have admitted the possibility of returning fees publicly, as Deephaven did in its filing with the S.E.C., it's a conversation that the funds are having with investors "under the radar" across the industry, says Larry Enkel, a partner in the hedge fund defense team for Morrison & Foerster.

"If you're trying to keep investors in because you're worried about a run, you have to send the signal that you're willing to make things right," he says. "The investors paid for what were essentially not real profits."

It's not clear how many hedge funds are in this particular predicament, but Zoia of Glocap says that it is becoming more common for hedge funds to collect fees more than once per year.

There's no telling just how the year will end for hedge funds or their investors, who may or may not have supplied an interest-free loan to their funds' managers during the happy days of early 2007.

But one thing both hedge funds and their investors can agree on is that 20 percent of nothing is, undeniably, still nothing.