A handful of the U.S.’s top performing, large hedge funds are opening their doors to fresh hires, reported Bloomberg. That list includes $34 billion Millennium Management, $25 billion Citadel, and $6.6 billion Visium Asset Management, which managed to bring in billions in new capital last year.

These hiring rounds come on the heels of a dismal 2015 for the financial industry, when unexpected market volatility forced several leading hedge funds, including a $2.3 billion Fortress Investment Group macro fund and Bain’s $2.2 billion macro fund to close. 673 funds closed in just the first three quarters of 2015, Hedge Fund Research told Bloomberg.

“There are some funds that are seizing the moment to take advantage of quality people who were in the wrong place at the wrong time,” said Gary Goldstein, head of executive search firm Whitney Partners to Bloomberg.

It’s expansion in an industry that seems on a course of contraction. Which raises the question—why are the hedge funds doing it?

According to Bloomberg, the hedge funds currently hiring all fall under one common denominator: Each firm relies on a trading style in which several small teams of traders work independently from each other to manage a portion of the fund’s assets.

Which means the hedge funds need more employees to manage a growing pool of assets.

These funds were also able to push through 2015 in part due to asset diversification stemming from their multi-management model, with assets not as concentrated within one sector, one stock, or even within one investment style.