These hedge-fund billionaires were the hottest hands in 2015

Consider 2015 to be the year the hedge-fund industry completed the crossover to the digital age.

Computerized trading strategies helped the nearly $3 trillion industry's biggest players reap the biggest profits. Fully six of the top eight moneymakers for the year use so-called quant approaches to generate profits.

Tops among them were Ken Griffin at Citadel and James Simons at Renaissance Technologies, both of whom reeled in $1.7 billion according to the year's Institutional Investor's Alpha Rich List of the top hedge fund managers. (Get the full top 25 list and analysis here.)

Overall, it was a tough slog for the industry. Returns were middling, with the HFRI fund weighted composite index falling 1 percent, only the fourth full-year decline since 1990. Assets, however, edged higher, rising $51.7 billion to $2.97 trillion, according to HFR.

It took less to make the Rich List, with the median income at $275 million, the lowest in five years. The average stood at $517,.6 million, a slight uptick from 2014 but off 40 percent from the $846 million in 2013. To be considered for inclusion on the list, managers had to make $135 million, the lowest since 2011.

Nearly half of hedge funds lost money, according to Institutional Investor, and some familiar names on the Rich Lists of years past were missing, including John Paulson of Paulson and Co., Leon Cooperman of Omega Advisors, and Daniel Loeb at Third Point.

These industry leaders , however, did make the list, and qualified for the top 10: