BOSTON (Reuters) - Billionaire hedge fund manager William Ackman, whose investment assets have shrunk by more than half in the last three years, has made a second round of staff cuts and laid off three investor relations team members, two sources familiar with the matter said on Tuesday.

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The prominent manager cut one investor relations executive and two investor services executives at his New York-based Pershing Square Capital Management hedge fund last week, the sources said. These layoffs come after Ackman cut his staff by 10 people in January, shrinking the firm to 46 employees from 56.

A spokesman for the firm declined to comment.

The fresh round of layoffs shows that Ackman, one of the industry’s most voluble activist investors, is moving forward with an overhaul that some had questioned but has so far been successful, involving both cost cuts and investment strategy changes.

Pershing Square now oversees roughly $8 billion in assets, less than half the amount it managed at its peak in 2015. Assets dwindled after three years of losses which prompted many investors to ask for some of their money back.

Unlike other managers who might try to replace departing capital, Ackman decided to re-tool his firm, telling clients that he wants to return to his roots by running a smaller firm and growing assets only through improved returns not by bringing in new investors.

In addition to the layoffs, key members of his team have voluntarily left.

Investment team member Ali Namvar retired and Vice Chairman Steve Fraidin returned to practicing law as a partner at Cadwalader, Wickersham & Taft.

Investment team member Brian Welch is leaving at the end of this month. The investment team has historically had between eight and 10 members.

In his early years, Ackman dazzled with double-digit returns, often delivering some of the industry’s best returns.

As part of the revamp, Ackman, one of the industry’s most visible managers, said he would stay out of the limelight to concentrate on investments, leaving the visiting with clients to others. So far this year the firm has made bets on Nike Inc, United Technologies Corp and Lowe’s Companies Inc.

So far Ackman’s promises of delivering improved returns appear to be materializing. Through the middle of June, Pershing Square’s private hedge fund was up more than 9 percent while the publicly traded fund, Pershing Square Holdings Ltd, was up 11.4 percent since the start of the year.