Hedge funds are the wild cards of financial markets. Some sharply criticize their activities, but others say they bring valuable diversity to markets and act as shock absorbers against volatility.

The sector saw it's best results since 2013 last year, producing an 8.5% return, up from 5.4% in 2016. But despite the stronger outlook, back-to-back losses in recent months caused by trade disputes, tech sector setbacks, and interest-rate hikes by the Federal Reserve have dampened returns.

Even in the midst of these adverse conditions hedge funds are still a formidable power, wielding billions of dollars in assets and significant influence in financial markets.

Data and research provider HFM Absolute Return created a list of the firms with the most in hedge fund assets in the US, ranked by assets under management (AUM). Many of the firms listed, including JPMorgan, Two Sigma and Bridgewater, have more in total assets under management, and hedge fund assets only represent a portion of their total asset management business.