For many firms, it was a whipsaw year, where strong gains were made in the first half of 2015 only to be reversed over the last six months. Investors in Mr. Ackman’s Pershing Square will be familiar with the queasy feeling those wild swings produce. A year ago, Pershing Square posted one of its best years, generating a nearly 40 percent return. As late as the first week of August, the firm’s main fund was up about 11 percent for the year. Since then, it has been on a downward trajectory, and big, concentrated bets on Valeant and Platform Specialty Products have tumbled.

As of Dec. 22, Pershing Square’s main public portfolio was down 19.5 percent for the year.

Other big losers in 2015 include Mr. Einhorn’s Greenlight Capital, which is down 20 percent, and Mr. Robbins’s Glenview Capital Management, which has lost 17 percent. The performance figures, through the end of November, were included in an HSBC report. And John A. Paulson, who made billions and a name for himself betting against the housing bubble, lost investors’ money in three funds through October.

Even with the dismal numbers, there were some rising stars. The average hedge fund, as measured by the Hedge Fund Research Composite Index, was up less than 1 percent. A small group outperformed against the backdrop of a disappointing year in equity and bond markets, with the S.&.P 500 down slightly heading into the final days of 2015.

Gabriel Plotkin, a former SAC Capital Advisors manager, and his hedge fund Melvin Capital was the industry outlier. Melvin Capital, a stock-focused hedge fund that started last year, had gained almost 40 percent by the middle of November, according to a person briefed on the fund’s performance who spoke on the condition of anonymity. Mr. Plotkin was one of the top consumer stock traders at SAC Capital Advisors, the former hedge fund founded by Steven A. Cohen.

Other notable hedge funds that look poised to make the top performing list this year include Israel Englander’s Millennium Management, which gained 11 percent through November, and Sahm Adrangi’s Kerrisdale Capital, which was up 18 percent in the same period, said people briefed on those firms’ performance numbers. Renaissance Technologies, founded by James H. Simons, and its two main funds were up more than 16 percent, according to a person with knowledge of the performance who spoke on the condition of anonymity.

A broad swath of firms also posted more modest gains in 2015, including Aaron Cowen’s Suvretta Capital Management, which was up 7 percent at the end of November, and Saba Capital Management, founded by Boaz Weinstein, which gained 6 percent through mid-December, according to people knowledgeable about those firms’ numbers.